PostGIS 2.0.2 Manual · PostGIS 2.0.2 Manual iii 3 PostGIS Frequently Asked Questions 20 4 Using PostGIS: Data Management and Queries24 4.1 GIS Objects

PostGIS 2.0.2 Manuali

PostGIS 2.0.2 Manual

SVN Revision (10793)

PostGIS 2.0.2 Manualii

Contents

1 Introduction 2

1.1 Project Steering Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Contributors Past and Present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 More Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Installation 5

2.1 Short Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3 Getting the Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4.1 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4.2 Building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.4.3 Building PostGIS Extensions and Deploying them . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.4.4 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.4.5 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.5 Create a spatially-enabled database on PostgreSQL lower than 9.1 . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.6 Creating a spatial database using EXTENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.7 Installing, Upgrading Tiger Geocoder and loading data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.7.1 Tiger Geocoder Enabling your PostGIS database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.7.2 Upgrading your Tiger Geocoder Install . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.7.3 Loading Tiger Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.8 Create a spatially-enabled database from a template . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.9 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.9.1 Soft upgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.9.1.1 Soft Upgrade Pre 9.1+ or without extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.9.1.2 Soft Upgrade 9.1+ using extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.9.2 Hard upgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.10 Common Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.11 JDBC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.12 Loader/Dumper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

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3 PostGIS Frequently Asked Questions 20

4 Using PostGIS: Data Management and Queries 24

4.1 GIS Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4.1.1 OpenGIS WKB and WKT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4.1.2 PostGIS EWKB, EWKT and Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.1.3 SQL-MM Part 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.2 PostGIS Geography Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2.1 Geography Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2.2 When to use Geography Data type over Geometry data type . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.3 Geography Advanced FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.3 Using OpenGIS Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.3.1 The SPATIAL_REF_SYS Table and Spatial Reference Systems . . . . . . . . . . . . . . . . . . . . . . 30

4.3.2 The GEOMETRY_COLUMNS VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.3.3 Creating a Spatial Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.3.4 Manually Registering Geometry Columns in geometry_columns . . . . . . . . . . . . . . . . . . . . . . 32

4.3.5 Ensuring OpenGIS compliancy of geometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.3.6 Dimensionally Extended 9 Intersection Model (DE-9IM) . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.3.6.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.4 Loading GIS Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.4.1 Using SQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.4.2 Using the Loader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.5 Retrieving GIS Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

4.5.1 Using SQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

4.5.2 Using the Dumper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

4.6 Building Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

4.6.1 GiST Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4.6.2 Using Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4.7 Complex Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.7.1 Taking Advantage of Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.7.2 Examples of Spatial SQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5 Raster Data Management, Queries, and Applications 52

5.1 Loading and Creating Rasters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.1.1 Using raster2pgsql to load rasters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.1.2 Creating rasters using PostGIS raster functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.2 Raster Catalogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.2.1 Raster Columns Catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.2.2 Raster Overviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

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5.3 Building Custom Applications with PostGIS Raster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.3.1 PHP Example Outputting using ST_AsPNG in concert with other raster functions . . . . . . . . . . . . . 58

5.3.2 ASP.NET C# Example Outputting using ST_AsPNG in concert with other raster functions . . . . . . . . 59

5.3.3 Java console app that outputs raster query as Image file . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

5.3.4 Use PLPython to dump out images via SQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

5.3.5 Outputting Rasters with PSQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6 Using PostGIS Geometry: Building Applications 64

6.1 Using MapServer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

6.1.1 Basic Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

6.1.2 Frequently Asked Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

6.1.3 Advanced Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

6.1.4 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

6.2 Java Clients (JDBC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

6.3 C Clients (libpq) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

6.3.1 Text Cursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

6.3.2 Binary Cursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7 Performance tips 70

7.1 Small tables of large geometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

7.1.1 Problem description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

7.1.2 Workarounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

7.2 CLUSTERing on geometry indices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

7.3 Avoiding dimension conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

7.4 Tuning your configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

7.4.1 Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

7.4.2 Runtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

8 PostGIS Reference 73

8.1 PostgreSQL PostGIS Geometry/Geography/Box Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

8.1.1 box2d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

8.1.2 box3d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

8.1.3 geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

8.1.4 geometry_dump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

8.1.5 geography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

8.2 Management Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

8.2.1 AddGeometryColumn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

8.2.2 DropGeometryColumn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.2.3 DropGeometryTable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

8.2.4 PostGIS_Full_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

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8.2.5 PostGIS_GEOS_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

8.2.6 PostGIS_LibXML_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

8.2.7 PostGIS_Lib_Build_Date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.2.8 PostGIS_Lib_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.2.9 PostGIS_PROJ_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

8.2.10 PostGIS_Scripts_Build_Date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

8.2.11 PostGIS_Scripts_Installed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

8.2.12 PostGIS_Scripts_Released . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

8.2.13 PostGIS_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

8.2.14 Populate_Geometry_Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

8.2.15 UpdateGeometrySRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

8.3 Geometry Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

8.3.1 ST_BdPolyFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

8.3.2 ST_BdMPolyFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

8.3.3 ST_GeogFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

8.3.4 ST_GeographyFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

8.3.5 ST_GeogFromWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

8.3.6 ST_GeomCollFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

8.3.7 ST_GeomFromEWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

8.3.8 ST_GeomFromEWKT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

8.3.9 ST_GeometryFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

8.3.10 ST_GeomFromGML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

8.3.11 ST_GeomFromGeoJSON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

8.3.12 ST_GeomFromKML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

8.3.13 ST_GMLToSQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

8.3.14 ST_GeomFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

8.3.15 ST_GeomFromWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

8.3.16 ST_LineFromMultiPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

8.3.17 ST_LineFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

8.3.18 ST_LineFromWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

8.3.19 ST_LinestringFromWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

8.3.20 ST_MakeBox2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

8.3.21 ST_3DMakeBox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

8.3.22 ST_MakeLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

8.3.23 ST_MakeEnvelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

8.3.24 ST_MakePolygon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

8.3.25 ST_MakePoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

8.3.26 ST_MakePointM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

8.3.27 ST_MLineFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

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8.3.28 ST_MPointFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

8.3.29 ST_MPolyFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

8.3.30 ST_Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

8.3.31 ST_PointFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

8.3.32 ST_PointFromWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

8.3.33 ST_Polygon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

8.3.34 ST_PolygonFromText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

8.3.35 ST_WKBToSQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

8.3.36 ST_WKTToSQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

8.4 Geometry Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

8.4.1 GeometryType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

8.4.2 ST_Boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

8.4.3 ST_CoordDim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

8.4.4 ST_Dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

8.4.5 ST_EndPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

8.4.6 ST_Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

8.4.7 ST_ExteriorRing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

8.4.8 ST_GeometryN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

8.4.9 ST_GeometryType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

8.4.10 ST_InteriorRingN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

8.4.11 ST_IsClosed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

8.4.12 ST_IsCollection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

8.4.13 ST_IsEmpty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

8.4.14 ST_IsRing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

8.4.15 ST_IsSimple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

8.4.16 ST_IsValid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

8.4.17 ST_IsValidReason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

8.4.18 ST_IsValidDetail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

8.4.19 ST_M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.4.20 ST_NDims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

8.4.21 ST_NPoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

8.4.22 ST_NRings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

8.4.23 ST_NumGeometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

8.4.24 ST_NumInteriorRings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

8.4.25 ST_NumInteriorRing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

8.4.26 ST_NumPatches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

8.4.27 ST_NumPoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

8.4.28 ST_PatchN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

8.4.29 ST_PointN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

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8.4.30 ST_SRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

8.4.31 ST_StartPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

8.4.32 ST_Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

8.4.33 ST_X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

8.4.34 ST_XMax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

8.4.35 ST_XMin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

8.4.36 ST_Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

8.4.37 ST_YMax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

8.4.38 ST_YMin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

8.4.39 ST_Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

8.4.40 ST_ZMax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

8.4.41 ST_Zmflag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

8.4.42 ST_ZMin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

8.5 Geometry Editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

8.5.1 ST_AddPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

8.5.2 ST_Affine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

8.5.3 ST_Force_2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

8.5.4 ST_Force_3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

8.5.5 ST_Force_3DZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

8.5.6 ST_Force_3DM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

8.5.7 ST_Force_4D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

8.5.8 ST_Force_Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

8.5.9 ST_ForceRHR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

8.5.10 ST_LineMerge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

8.5.11 ST_CollectionExtract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

8.5.12 ST_CollectionHomogenize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

8.5.13 ST_Multi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

8.5.14 ST_RemovePoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

8.5.15 ST_Reverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

8.5.16 ST_Rotate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

8.5.17 ST_RotateX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

8.5.18 ST_RotateY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

8.5.19 ST_RotateZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

8.5.20 ST_Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

8.5.21 ST_Segmentize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

8.5.22 ST_SetPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

8.5.23 ST_SetSRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

8.5.24 ST_SnapToGrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

8.5.25 ST_Snap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

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8.5.26 ST_Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

8.5.27 ST_Translate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

8.5.28 ST_TransScale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

8.6 Geometry Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

8.6.1 ST_AsBinary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

8.6.2 ST_AsEWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

8.6.3 ST_AsEWKT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

8.6.4 ST_AsGeoJSON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

8.6.5 ST_AsGML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

8.6.6 ST_AsHEXEWKB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

8.6.7 ST_AsKML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

8.6.8 ST_AsSVG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

8.6.9 ST_AsX3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

8.6.10 ST_GeoHash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

8.6.11 ST_AsText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

8.6.12 ST_AsLatLonText . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

8.7 Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

8.7.1 && . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

8.7.2 &&& . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

8.7.3 &< . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

8.7.4 &<| . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

8.7.5 &> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

8.7.6 << . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

8.7.7 <<| . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

8.7.8 = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

8.7.9 >> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

8.7.10 @ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

8.7.11 |&> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

8.7.12 |>> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

8.7.13 ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

8.7.14 ~= . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

8.7.15 <-> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

8.7.16 <#> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

8.8 Spatial Relationships and Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

8.8.1 ST_3DClosestPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

8.8.2 ST_3DDistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

8.8.3 ST_3DDWithin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

8.8.4 ST_3DDFullyWithin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

8.8.5 ST_3DIntersects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

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8.8.6 ST_3DLongestLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

8.8.7 ST_3DMaxDistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

8.8.8 ST_3DShortestLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

8.8.9 ST_Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

8.8.10 ST_Azimuth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

8.8.11 ST_Centroid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

8.8.12 ST_ClosestPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

8.8.13 ST_Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

8.8.14 ST_ContainsProperly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

8.8.15 ST_Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

8.8.16 ST_CoveredBy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

8.8.17 ST_Crosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

8.8.18 ST_LineCrossingDirection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

8.8.19 ST_Disjoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

8.8.20 ST_Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

8.8.21 ST_HausdorffDistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

8.8.22 ST_MaxDistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

8.8.23 ST_Distance_Sphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

8.8.24 ST_Distance_Spheroid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

8.8.25 ST_DFullyWithin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

8.8.26 ST_DWithin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

8.8.27 ST_Equals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

8.8.28 ST_HasArc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

8.8.29 ST_Intersects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

8.8.30 ST_Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

8.8.31 ST_Length2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

8.8.32 ST_3DLength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

8.8.33 ST_Length_Spheroid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

8.8.34 ST_Length2D_Spheroid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

8.8.35 ST_3DLength_Spheroid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

8.8.36 ST_LongestLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

8.8.37 ST_OrderingEquals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

8.8.38 ST_Overlaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

8.8.39 ST_Perimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

8.8.40 ST_Perimeter2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

8.8.41 ST_3DPerimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

8.8.42 ST_PointOnSurface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

8.8.43 ST_Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

8.8.44 ST_Relate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

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8.8.45 ST_RelateMatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

8.8.46 ST_ShortestLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

8.8.47 ST_Touches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

8.8.48 ST_Within . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

8.9 Geometry Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

8.9.1 ST_Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

8.9.2 ST_BuildArea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278

8.9.3 ST_Collect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

8.9.4 ST_ConcaveHull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

8.9.5 ST_ConvexHull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

8.9.6 ST_CurveToLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

8.9.7 ST_Difference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

8.9.8 ST_Dump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

8.9.9 ST_DumpPoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

8.9.10 ST_DumpRings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

8.9.11 ST_FlipCoordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

8.9.12 ST_Intersection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

8.9.13 ST_LineToCurve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

8.9.14 ST_MakeValid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

8.9.15 ST_MemUnion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

8.9.16 ST_MinimumBoundingCircle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

8.9.17 ST_Polygonize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

8.9.18 ST_Node . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

8.9.19 ST_OffsetCurve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

8.9.20 ST_RemoveRepeatedPoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

8.9.21 ST_SharedPaths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

8.9.22 ST_Shift_Longitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

8.9.23 ST_Simplify . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

8.9.24 ST_SimplifyPreserveTopology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

8.9.25 ST_Split . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

8.9.26 ST_SymDifference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

8.9.27 ST_Union . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

8.9.28 ST_UnaryUnion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

8.10 Linear Referencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

8.10.1 ST_Line_Interpolate_Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

8.10.2 ST_Line_Locate_Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

8.10.3 ST_Line_Substring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

8.10.4 ST_LocateAlong . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

8.10.5 ST_LocateBetween . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

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8.10.6 ST_LocateBetweenElevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

8.10.7 ST_InterpolatePoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

8.10.8 ST_AddMeasure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

8.11 Long Transactions Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

8.11.1 AddAuth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

8.11.2 CheckAuth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

8.11.3 DisableLongTransactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

8.11.4 EnableLongTransactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

8.11.5 LockRow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

8.11.6 UnlockRows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

8.12 Miscellaneous Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

8.12.1 ST_Accum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

8.12.2 Box2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

8.12.3 Box3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

8.12.4 ST_Estimated_Extent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

8.12.5 ST_Expand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

8.12.6 ST_Extent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

8.12.7 ST_3DExtent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

8.12.8 Find_SRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

8.12.9 ST_Mem_Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

8.12.10 ST_Point_Inside_Circle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

8.13 Exceptional Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

8.13.1 PostGIS_AddBBox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

8.13.2 PostGIS_DropBBox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

8.13.3 PostGIS_HasBBox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

9 Raster Reference 346

9.1 Raster Support Data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

9.1.1 geomval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

9.1.2 histogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

9.1.3 raster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

9.1.4 reclassarg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

9.1.5 summarystats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

9.2 Raster Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

9.2.1 AddRasterConstraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

9.2.2 DropRasterConstraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

9.2.3 PostGIS_Raster_Lib_Build_Date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

9.2.4 PostGIS_Raster_Lib_Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

9.2.5 ST_GDALDrivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

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9.3 Raster Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

9.3.1 ST_AddBand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

9.3.2 ST_AsRaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358

9.3.3 ST_Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

9.3.4 ST_MakeEmptyRaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

9.4 Raster Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

9.4.1 ST_GeoReference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

9.4.2 ST_Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363

9.4.3 ST_MetaData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

9.4.4 ST_NumBands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

9.4.5 ST_PixelHeight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

9.4.6 ST_PixelWidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

9.4.7 ST_ScaleX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

9.4.8 ST_ScaleY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

9.4.9 ST_Raster2WorldCoordX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

9.4.10 ST_Raster2WorldCoordY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369

9.4.11 ST_Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370

9.4.12 ST_SkewX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370

9.4.13 ST_SkewY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

9.4.14 ST_SRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

9.4.15 ST_UpperLeftX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

9.4.16 ST_UpperLeftY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

9.4.17 ST_Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

9.4.18 ST_World2RasterCoordX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

9.4.19 ST_World2RasterCoordY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

9.4.20 ST_IsEmpty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

9.5 Raster Band Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

9.5.1 ST_BandMetaData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

9.5.2 ST_BandNoDataValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

9.5.3 ST_BandIsNoData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

9.5.4 ST_BandPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378

9.5.5 ST_BandPixelType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379

9.5.6 ST_HasNoBand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380

9.6 Raster Pixel Accessors and Setters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380

9.6.1 ST_PixelAsPolygon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380

9.6.2 ST_PixelAsPolygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

9.6.3 ST_Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382

9.6.4 ST_SetValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384

9.7 Raster Editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385

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9.7.1 ST_SetGeoReference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385

9.7.2 ST_SetRotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

9.7.3 ST_SetScale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

9.7.4 ST_SetSkew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388

9.7.5 ST_SetSRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

9.7.6 ST_SetUpperLeft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

9.7.7 ST_Resample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390

9.7.8 ST_Rescale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

9.7.9 ST_Reskew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

9.7.10 ST_SnapToGrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

9.7.11 ST_Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394

9.8 Raster Band Editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

9.8.1 ST_SetBandNoDataValue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

9.8.2 ST_SetBandIsNoData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

9.9 Raster Band Statistics and Analytics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

9.9.1 ST_Count . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

9.9.2 ST_Histogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

9.9.3 ST_Quantile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

9.9.4 ST_SummaryStats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403

9.9.5 ST_ValueCount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405

9.10 Raster Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

9.10.1 ST_AsBinary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

9.10.2 ST_AsGDALRaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

9.10.3 ST_AsJPEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409

9.10.4 ST_AsPNG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409

9.10.5 ST_AsTIFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410

9.11 Raster Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411

9.11.1 Box3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411

9.11.2 ST_Clip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412

9.11.3 ST_ConvexHull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414

9.11.4 ST_DumpAsPolygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415

9.11.5 ST_Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

9.11.6 ST_HillShade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

9.11.7 ST_Aspect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

9.11.8 ST_Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418

9.11.9 ST_Intersection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419

9.11.10 ST_MapAlgebraExpr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

9.11.11 ST_MapAlgebraExpr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

9.11.12 ST_MapAlgebraFct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

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9.11.13 ST_MapAlgebraFct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430

9.11.14 ST_MapAlgebraFctNgb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

9.11.15 ST_Polygon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436

9.11.16 ST_Reclass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

9.11.17 ST_Union . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439

9.12 Raster Processing Builtin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440

9.12.1 ST_Min4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440

9.12.2 ST_Max4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

9.12.3 ST_Sum4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442

9.12.4 ST_Mean4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443

9.12.5 ST_Range4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443

9.12.6 ST_Distinct4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444

9.12.7 ST_StdDev4ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445

9.13 Raster Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

9.13.1 && . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

9.13.2 &< . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

9.13.3 &> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447

9.14 Raster and Raster Band Spatial Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448

9.14.1 ST_Intersects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448

9.14.2 ST_SameAlignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449

10 PostGIS Raster Frequently Asked Questions 450

11 Topology 454

11.1 Topology Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454

11.1.1 getfaceedges_returntype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454

11.1.2 TopoGeometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455

11.1.3 validatetopology_returntype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455

11.2 Topology Domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

11.2.1 TopoElement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

11.2.2 TopoElementArray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

11.3 Topology and TopoGeometry Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457

11.3.1 AddTopoGeometryColumn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457

11.3.2 DropTopology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

11.3.3 DropTopoGeometryColumn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

11.3.4 TopologySummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459

11.3.5 ValidateTopology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459

11.4 Topology Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460

11.4.1 CreateTopology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460

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11.4.2 CopyTopology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

11.4.3 ST_InitTopoGeo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

11.4.4 ST_CreateTopoGeo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

11.4.5 TopoGeo_AddPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

11.4.6 TopoGeo_AddLineString . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

11.4.7 TopoGeo_AddPolygon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

11.5 Topology Editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

11.5.1 ST_AddIsoNode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

11.5.2 ST_AddIsoEdge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

11.5.3 ST_AddEdgeNewFaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465

11.5.4 ST_AddEdgeModFace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

11.5.5 ST_RemEdgeNewFace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

11.5.6 ST_RemEdgeModFace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

11.5.7 ST_ChangeEdgeGeom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

11.5.8 ST_ModEdgeSplit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468

11.5.9 ST_ModEdgeHeal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469

11.5.10 ST_NewEdgeHeal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469

11.5.11 ST_MoveIsoNode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470

11.5.12 ST_NewEdgesSplit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

11.5.13 ST_RemoveIsoNode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

11.6 Topology Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472

11.6.1 GetEdgeByPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472

11.6.2 GetFaceByPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473

11.6.3 GetNodeByPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474

11.6.4 GetTopologyID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475

11.6.5 GetTopologySRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475

11.6.6 GetTopologyName . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476

11.6.7 ST_GetFaceEdges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476

11.6.8 ST_GetFaceGeometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477

11.6.9 GetRingEdges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478

11.6.10 GetNodeEdges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478

11.7 Topology Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

11.7.1 Polygonize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

11.7.2 AddNode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

11.7.3 AddEdge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480

11.7.4 AddFace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481

11.8 TopoGeometry Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483

11.8.1 CreateTopoGeom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483

11.8.2 toTopoGeom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

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11.8.3 TopoElementArray_Agg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

11.9 TopoGeometry Accessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

11.9.1 GetTopoGeomElementArray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

11.9.2 GetTopoGeomElements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

11.10TopoGeometry Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

11.10.1 AsGML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

12 PostGIS Extras 490

12.1 Tiger Geocoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

12.1.1 Drop_Indexes_Generate_Script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

12.1.2 Drop_State_Tables_Generate_Script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

12.1.3 Geocode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

12.1.4 Geocode_Intersection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

12.1.5 Get_Tract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

12.1.6 Install_Missing_Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496

12.1.7 Loader_Generate_Script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496

12.1.8 Loader_Generate_Census_Script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498

12.1.9 Missing_Indexes_Generate_Script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500

12.1.10 Normalize_Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500

12.1.11 Pprint_Addy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502

12.1.12 Reverse_Geocode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502

12.1.13 Topology_Load_Tiger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504

13 PostGIS Special Functions Index 507

13.1 PostGIS Aggregate Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507

13.2 PostGIS SQL-MM Compliant Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

13.3 PostGIS Geography Support Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512

13.4 PostGIS Raster Support Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

13.5 PostGIS Geometry / Geography / Raster Dump Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517

13.6 PostGIS Box Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517

13.7 PostGIS Functions that support 3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518

13.8 PostGIS Curved Geometry Support Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522

13.9 PostGIS Polyhedral Surface Support Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

13.10PostGIS Function Support Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526

13.11New, Enhanced or changed PostGIS Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533

13.11.1 PostGIS Functions new, behavior changed, or enhanced in 2.0 . . . . . . . . . . . . . . . . . . . . . . . 533

13.11.2 PostGIS Functions changed behavior in 2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541



13.11.5 PostGIS Functions new in 1.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545

PostGIS 2.0.2 Manualxvii

14 Reporting Problems 546

14.1 Reporting Software Bugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546

14.2 Reporting Documentation Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546

A Appendix 547

A.1 Release 2.0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

A.1.1 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

A.1.2 Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

A.2 Release 2.0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

A.2.1 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

A.2.2 Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549

A.3 Release 2.0.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

A.3.1 Testers - Our unsung heroes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

A.3.2 Important / Breaking Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

A.3.3 New Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

A.3.4 Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

A.3.5 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

A.3.6 Release specific credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

A.4 Release 1.5.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552

A.4.1 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552

A.5 Release 1.5.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552

A.5.1 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

A.6 Release 1.5.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

A.6.1 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

A.7 Release 1.5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

A.7.1 Bug Fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

A.8 Release 1.5.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

A.8.1 API Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

A.8.2 Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

A.8.3 New Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

A.8.4 Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

A.8.5 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

A.9 Release 1.4.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

A.9.1 API Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

A.9.2 Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

A.9.3 New Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

A.9.4 Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

A.9.5 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

A.10 Release 1.3.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

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A.11 Release 1.3.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

A.12 Release 1.3.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.13 Release 1.3.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.14 Release 1.3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.15 Release 1.3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.16 Release 1.3.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.16.1 Added Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.16.2 Performance Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

A.16.3 Other Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.17 Release 1.2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.17.1 Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.18 Release 1.2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.18.1 Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.19 Release 1.1.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.19.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

A.19.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.19.3 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.20 Release 1.1.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.20.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.20.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.20.3 New Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.21 Release 1.1.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560

A.21.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561

A.21.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561

A.21.3 Java changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561

A.22 Release 1.1.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561

A.22.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561

A.22.2 Bug fixes / correctness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561

A.22.3 New functionalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562

A.22.4 JDBC changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562

A.22.5 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562

A.23 Release 1.1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562

A.23.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562

A.23.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562


A.23.4 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563

A.24 Release 1.1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563

A.24.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563

A.24.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563

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A.25 Release 1.1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

A.25.1 Credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

A.25.2 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

A.25.3 New functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

A.25.4 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

A.25.5 Function semantic changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

A.25.6 Performance improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

A.25.7 JDBC2 works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

A.25.8 Other new things . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

A.25.9 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

A.26 Release 1.0.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

A.26.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

A.26.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

A.26.3 Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

A.27 Release 1.0.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

A.27.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

A.27.2 Library changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567

A.27.3 Loader changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567

A.27.4 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567

A.28 Release 1.0.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567

A.28.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567

A.28.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567

A.28.3 Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

A.29 Release 1.0.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

A.29.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

A.29.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

A.29.3 Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

A.30 Release 1.0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

A.30.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

A.30.2 Bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

A.30.3 Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

A.31 Release 1.0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

A.31.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569


A.31.3 Other changes/additions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

A.32 Release 1.0.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570

A.32.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570


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A.32.3 Other changes/additions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570

A.33 Release 1.0.0RC6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570

A.33.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570


A.33.3 Scripts changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570

A.33.4 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571

A.34 Release 1.0.0RC5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571

A.34.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571


A.34.3 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571

A.35 Release 1.0.0RC4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571

A.35.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571



A.35.4 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572

A.36 Release 1.0.0RC3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572

A.36.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572



A.36.4 JDBC changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573

A.36.5 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573

A.37 Release 1.0.0RC2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573

A.37.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573



A.37.4 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574

A.38 Release 1.0.0RC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574

A.38.1 Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574

A.38.2 Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574

Abstract

PostGIS is an extension to the PostgreSQL object-relational database system which allows GIS (Geographic Information Sys-tems) objects to be stored in the database. PostGIS includes support for GiST-based R-Tree spatial indexes, and functions foranalysis and processing of GIS objects.

This is the manual for version 2.0.2

This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Feel free to usethis material any way you like, but we ask that you attribute credit to the PostGIS Project and wherever possible, a link back tohttp://www.postgis.org.

http://creativecommons.org/licenses/by-sa/3.0/

http://www.postgis.org

PostGIS 2.0.2 Manual1 / 574

SVN Revision (10793)


Chapter 1

Introduction

PostGIS was developed by Refractions Research Inc, as a spatial database technology research project. Refractions is a GISand database consulting company in Victoria, British Columbia, Canada, specializing in data integration and custom softwaredevelopment. We plan on supporting and developing PostGIS to support a range of important GIS functionality, including fullOpenGIS support, advanced topological constructs (coverages, surfaces, networks), desktop user interface tools for viewing andediting GIS data, and web-based access tools.

PostGIS is an incubation project of the OSGeo Foundation. PostGIS is being continually improved and funded by many FOSS4GDevelopers as well as corporations all over the world that gain great benefit from its functionality and versatility.

1.1 Project Steering Committee

The PostGIS Project Steering Committee (PSC) coordinates the general direction, release cycles, documentation, and outreachefforts for the PostGIS project. In addition the PSC provides general user support, accepts and approves patches from the generalPostGIS community and votes on miscellaneous issues involving PostGIS such as developer commit access, new PSC membersor significant API changes.

Mark Cave-Ayland Coordinates bug fixing and maintenance effort, alignment of PostGIS with PostgreSQL releases, spatial in-dex selectivity and binding, loader/dumper, and Shapefile GUI Loader, integration of new and new function enhancements.

Chris Hodgson General development, site and buildbot maintenance, OSGeo incubation management

Regina Obe Documentation, general user support on PostGIS newsgroup, windows production and experimental builds, X3Dsupport, Tiger Geocoder Support, management functions, and smoke testing new functionality or major code changes.

Paul Ramsey (Chair) Co-founder of PostGIS project. General bug fixing, geography support, geography and geometry indexsupport (2D, 3D, nD index and anything spatial index), underlying geometry internal structures, GEOS functionalityintegration and alignment with GEOS releases, loader/dumper, and Shapefile GUI loader.

Sandro Santilli Bug fixes and maintenance and integration of new GEOS functionality and alignment with GEOS releases,Topology support, and Raster framework and low level api functions.

1.2 Contributors Past and Present

Kevin Neufeld Prior PSC Member. Documentation and documentation support tools, advanced user support on PostGIS news-group, and PostGIS maintenance function enhancements.

Dave Blasby The original developer/Co-founder of PostGIS. Dave wrote the server side objects, index bindings, and many ofthe server side analytical functions.


Jeff Lounsbury Original development of the Shape file loader/dumper. Current PostGIS Project Owner representative.

Olivier Courtin Input output XML (KML,GML)/GeoJSON functions, 3D support and bug fixes.

Mark Leslie Ongoing maintenance and development of core functions. Enhanced curve support. Shapefile GUI loader.

Pierre Racine Raster overall architecture, prototyping, programming support

Nicklas Avén Distance function enhancements (including 3D distance and relationship functions) and additions, Windows test-ing, and general user support

Jorge Arévalo Raster development, GDAL driver support, loader

Bborie Park Raster development

Mateusz Loskot Raster loader, low level raster api functions

David Zwarg Raster development

Other contributors: Individuals In alphabetical order: Alex Bodnaru, Alex Mayrhofer, Andrea Peri, Andreas Forø Tollefsen,Andreas Neumann, Anne Ghisla, Barbara Phillipot, Ben Jubb, Bernhard Reiter, Brian Hamlin, Bruce Rindahl, Bruno WolffIII, Bryce L. Nordgren, Carl Anderson, Charlie Savage, Dane Springmeyer, David Skea, David Techer, Eduin Carrillo,Even Rouault, Frank Warmerdam, George Silva, Gerald Fenoy, Gino Lucrezi, Guillaume Lelarge, IIDA Tetsushi, IngvildNystuen, Jeff Adams, Jose Carlos Martinez Llari, Kashif Rasul, Klaus Foerster, Kris Jurka, Leo Hsu, Loic Dachary, Luca S.Percich, Maria Arias de Reyna, Mark Sondheim, Markus Schaber, Maxime Guillaud, Maxime van Noppen, Michael Fuhr,Nikita Shulga, Norman Vine, Rafal Magda, Ralph Mason, Richard Greenwood, Silvio Grosso, Steffen Macke, StephenFrost, Tom van Tilburg, Vincent Picavet

Other contributors: Corporate Sponsors These are corporate entities that have contributed developer time, hosting, or directmonetary funding to the PostGIS projectIn alphabetical order: Arrival 3D, Associazione Italiana per l’Informazione Geografica Libera (GFOSS.it), AusVet, Aven-cia, Azavea, Cadcorp, CampToCamp, City of Boston (DND), Clever Elephant Solutions, Cooperativa Alveo, DeimosSpace, Faunalia, Geographic Data BC, Hunter Systems Group, Lidwala Consulting Engineers, LisaSoft, Logical Track-ing & Tracing International AG, Michigan Tech Research Institute, Norwegian Forest and Landscape Institute, OpenGeo,OSGeo, Oslandia, Paragon Corporation, R3 GIS„ Refractions Research, Regione Toscana-SIGTA, Safe Software, SiriusCorporation plc, Stadt Uster, UC Davis Center for Vectorborne Diseases, University of Laval, U.S Department of State(HIU), Vizzuality, Zonar Systems

Crowd Funding Campaigns Crowd funding campaigns are campaigns we run to get badly wanted features funded that canservice a large number of people. Each campaign is specifically focused on a particular feature or set of features. Eachsponsor chips in a small fraction of the needed funding and with enough people/organizations contributing, we have thefunds to pay for the work that will help many. If you have an idea for a feature you think many others would be willing toco-fund, please post to the PostGIS newsgroup your thoughts and together we can make it happen.PostGIS 2.0.0 was the first release we tried this strategy. We used PledgeBank and we got two successful campaigns outof it.postgistopology - 10 plus sponsors each contributed $250 USD to build toTopoGeometry function and beef up topologysupport in 2.0.0. It happened.postgis64windows - 20 someodd sponsors each contributed $100 USD to pay for the work needed to work out PostGIS64-bit on windows issues. It happened. We now have a 64-bit beta release for PostGIS 2.0.0 and a final one planned forrelease that will be available on PostgreSQL stack builder.

Important Support Libraries The GEOS geometry operations library, and the algorithmic work of Martin Davis in making itall work, ongoing maintenance and support of Mateusz Loskot, Sandro Santilli (strk), Paul Ramsey and others.The GDAL Geospatial Data Abstraction Library, by Frank Warmerdam and others is used to power much of the rasterfunctionality introduced in PostGIS 2.0.0. In kind, improvements needed in GDAL to support PostGIS are contributedback to the GDAL project.The Proj4 cartographic projection library, and the work of Gerald Evenden and Frank Warmerdam in creating and main-taining it.Last but not least, the PostgreSQL DBMS, The giant that PostGIS stands on. Much of the speed and flexibility of PostGISwould not be possible without the extensibility, great query planner, GIST index, and plethora of SQL features providedby PostgreSQL.

http://www.postgis.org/mailman/listinfo/postgis-users

http://www.pledgebank.com

http://www.pledgebank.com/postgistopology

http://www.pledgebank.com/postgis64windows

http://trac.osgeo.org/geos/

http://trac.osgeo.org/gdal/

http://trac.osgeo.org/proj/

http://www.postgresql.org


1.3 More Information

• The latest software, documentation and news items are available at the PostGIS web site, http://www.postgis.org.

• More information about the GEOS geometry operations library is available athttp://trac.osgeo.org/geos/.

• More information about the Proj4 reprojection library is available at http://trac.osgeo.org/proj/.

• More information about the PostgreSQL database server is available at the PostgreSQL main site http://www.postgresql.org.

• More information about GiST indexing is available at the PostgreSQL GiST development site, http://www.sai.msu.su/~megera/-postgres/gist/.

• More information about MapServer internet map server is available at http://mapserver.org.

• The "Simple Features for Specification for SQL" is available at the OpenGIS Consortium web site: http://www.opengeospatial.org/-.

http://www.postgis.org




http://www.sai.msu.su/~megera/postgres/gist/

http://www.sai.msu.su/~megera/postgres/gist/

http://mapserver.org/

http://www.opengeospatial.org/standards/sfs

http://www.opengeospatial.org/



Chapter 2

Installation

This chapter details the steps required to install PostGIS.

2.1 Short Version

NoteThe raster support is currently optional, but installed by default. For installing using the PostgreSQL 9.1+ extensionsmodel it is required. Please refer to Section 2.4.3 if you are using PostgreSQL 9.1+.

All the .sql files once installed will be installed in share/contrib/postgis-2.0 folder of your PostgreSQL install

The postgis_comments.sql, raster_comments.sql, topology_comments.sql generate quick help tips foreach function that can be accessed via pgAdmin III or psql. In psql with a command of the form e.g.\dd ST_SetPoint

tar xvfz postgis-2.0.2.tar.gzcd postgis-2.0.2./configure --with-raster --with-topology --with-guimakemake installcreatedb yourdatabasecreatelang plpgsql yourdatabasepsql -d yourdatabase -f postgis.sqlpsql -d yourdatabase -f postgis_comments.sqlpsql -d yourdatabase -f spatial_ref_sys.sqlpsql -d yourdatabase -f rtpostgis.sqlpsql -d yourdatabase -f raster_comments.sqlpsql -d yourdatabase -f topology/topology.sqlpsql -d yourdatabase -f doc/topology_comments.sql

Notetopology_comments.sql since its an optional feature is not installed by make install or make comments install. Howeverif you do a make comments or make topology_comments.sql, it will be generated in the docs folder

The rest of this chapter goes into detail each of the above installation steps.


2.2 Requirements

PostGIS has the following requirements for building and usage:

Required

• PostgreSQL 8.4 or higher. A complete installation of PostgreSQL (including server headers) is required. PostgreSQL isavailable from http://www.postgresql.org .

For a full PostgreSQL / PostGIS support matrix and PostGIS/GEOS support matrix refer to http://trac.osgeo.org/postgis/wiki/-UsersWikiPostgreSQLPostGIS

• GNU C compiler (gcc). Some other ANSI C compilers can be used to compile PostGIS, but we find far fewer problems whencompiling with gcc.

• GNU Make (gmake or make). For many systems, GNU make is the default version of make. Check the version by invokingmake -v. Other versions of make may not process the PostGIS Makefile properly.

• Proj4 reprojection library, version 4.6.0 or greater. The Proj4 library is used to provide coordinate reprojection support withinPostGIS. Proj4 is available for download from http://trac.osgeo.org/proj/ .

• GEOS geometry library, version 3.2.2 or greater, but GEOS 3.3.2+ is recommended. Without GEOS 3.3, you will be missingsome major enhancements with handling of topological exceptions and improvements to geometry validation and makinggeometries valid such as ST_ValidDetail and ST_MakeValid. GEOS 3.3.2+ is also required for topology support. GEOS isavailable for download from http://trac.osgeo.org/geos/ and 3.3+ is backward-compatible with older versions so fairly safe toupgrade.

• LibXML2, version 2.5.x or higher. LibXML2 is currently used in some imports functions (ST_GeomFromGML and ST_GeomFromKML).LibXML2 is available for download from http://xmlsoft.org/downloads.html.

• JSON-C, version 0.9 or higher. JSON-C is currently used to import GeoJSON via the function ST_GeomFromGeoJson.JSON-C is available for download from http://oss.metaparadigm.com/json-c/.

• GDAL, version 1.6 or higher (1.9 or higher is preferable since some things will not work well with lower versions). This isneeded for raster support and will be required in final release of PostGIS 2.0. http://trac.osgeo.org/gdal/wiki/DownloadSource.

Optional

• GTK (requires GTK+2.0 (2.8+)) to compile the shp2pgsql-gui shape file loader. http://www.gtk.org/ .

• CUnit (CUnit). This is needed for regression testing. http://cunit.sourceforge.net/

• Apache Ant (ant) is required for building any of the drivers under the java directory. Ant is available from http://ant.apache.org.

• DocBook (xsltproc) is required for building the documentation. Docbook is available from http://www.docbook.org/ .

• DBLatex (dblatex) is required for building the documentation in PDF format. DBLatex is available from http://dblatex.sourceforge.net/-.

• ImageMagick (convert) is required to generate the images used in the documentation. ImageMagick is available fromhttp://www.imagemagick.org/ .

2.3 Getting the Source

Retrieve the PostGIS source archive from the downloads website http://www.postgis.org/download/postgis-2.0.2.tar.gz

wget http://www.postgis.org/download/postgis-2.0.2.tar.gztar -xvzf postgis-2.0.2.tar.gz


http://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS

http://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS



http://xmlsoft.org/downloads.html

http://oss.metaparadigm.com/json-c/

http://trac.osgeo.org/gdal/wiki/DownloadSource

http://www.gtk.org/

http://cunit.sourceforge.net/

http://ant.apache.org

http://ant.apache.org

http://www.docbook.org/

http://dblatex.sourceforge.net/

http://dblatex.sourceforge.net/

http://www.imagemagick.org/

http://www.postgis.org/download/postgis-2.0.2.tar.gz


This will create a directory called postgis-2.0.2 in the current working directory.

Alternatively, checkout the source from the svn repository http://svn.osgeo.org/postgis/branches/2.0 .

svn checkout http://svn.osgeo.org/postgis/branches/2.0/ postgis-2.0.2

Change into the newly created postgis-2.0.2 directory to continue the installation.

2.4 Installation

NoteMany OS systems now include pre-built packages for PostgreSQL/PostGIS. In many cases compilation is only neces-sary if you want the most bleeding edge versions or you are a package maintainer.This section includes general compilation instructions, if you are compiling for Windows etc or another OS, you mayfind additional more detailed help at PostGIS User contributed compile/install guides and PostGIS Dev Wiki.Pre-Built Packages for various OS are listed in PostGIS Pre-built Packages.If you are a windows user, you can get stable builds via Stackbuilder or PostGIS Windows download site We alsohave very bleeding-edge windows experimental builds that are built usually once or twice a week or whenever anythingexciting happens. You can use these to experiment with the in progress releases of PostGIS

The PostGIS module is an extension to the PostgreSQL backend server. As such, PostGIS 2.0.2 requires full PostgreSQL serverheaders access in order to compile. It can be built against PostgreSQL versions 8.4 or higher. Earlier versions of PostgreSQL arenot supported.

Refer to the PostgreSQL installation guides if you haven’t already installed PostgreSQL. http://www.postgresql.org .

NoteFor GEOS functionality, when you install PostgresSQL you may need to explicitly link PostgreSQL against the standardC++ library:

LDFLAGS=-lstdc++ ./configure [YOUR OPTIONS HERE]

This is a workaround for bogus C++ exceptions interaction with older development tools. If you experience weirdproblems (backend unexpectedly closed or similar things) try this trick. This will require recompiling your PostgreSQLfrom scratch, of course.

The following steps outline the configuration and compilation of the PostGIS source. They are written for Linux users and willnot work on Windows or Mac.

2.4.1 Configuration

As with most linux installations, the first step is to generate the Makefile that will be used to build the source code. This is doneby running the shell script

./configure

With no additional parameters, this command will attempt to automatically locate the required components and libraries neededto build the PostGIS source code on your system. Although this is the most common usage of ./configure, the script acceptsseveral parameters for those who have the required libraries and programs in non-standard locations.

The following list shows only the most commonly used parameters. For a complete list, use the --help or --help=short parame-ters.

--prefix=PREFIX This is the location the PostGIS libraries and SQL scripts will be installed to. By default, this location is thesame as the detected PostgreSQL installation.

http://subversion.apache.org/

http://svn.osgeo.org/postgis/branches/2.0

http://trac.osgeo.org/postgis/wiki/UsersWikiInstall

http://trac.osgeo.org/postgis/wiki/DevWikiMain

http://trac.osgeo.org/postgis/wiki/UsersWikiPackages

http://www.postgis.org/download/windows/

http://www.postgis.org/download/windows/experimental.php



CautionThis parameter is currently broken, as the package will only install into the PostgreSQL installation directory. Visithttp://trac.osgeo.org/postgis/ticket/635 to track this bug.

--with-pgconfig=FILE PostgreSQL provides a utility called pg_config to enable extensions like PostGIS to locate the Post-greSQL installation directory. Use this parameter (--with-pgconfig=/path/to/pg_config) to manually specify a particularPostgreSQL installation that PostGIS will build against.

--with-gdalconfig=FILE GDAL, a required library, provides functionality needed for raster support gdal-config to enable soft-ware installations to locate the GDAL installation directory. Use this parameter (--with-gdalconfig=/path/to/gdal-config)to manually specify a particular GDAL installation that PostGIS will build against.

--with-geosconfig=FILE GEOS, a required geometry library, provides a utility called geos-config to enable software installa-tions to locate the GEOS installation directory. Use this parameter (--with-geosconfig=/path/to/geos-config) to manuallyspecify a particular GEOS installation that PostGIS will build against.

--with-xml2config=FILE LibXML is the library required for doing GeomFromKML/GML processes. It normally is foundif you have libxml installed, but if not or you want a specific version used, you’ll need to point PostGIS at a specificxml2-config confi file to enable software installations to locate the LibXML installation directory. Use this parameter(>--with-xml2config=/path/to/xml2-config) to manually specify a particular LibXML installation that PostGIS will buildagainst.

--with-projdir=DIR Proj4 is a reprojection library required by PostGIS. Use this parameter (--with-projdir=/path/to/projdir)to manually specify a particular Proj4 installation directory that PostGIS will build against.

--with-libiconv=DIR Directory where iconv is installed.

--with-jsondir=DIR JSON-C is an MIT-licensed JSON library required by PostGIS ST_GeomFromJSON support. Use thisparameter (--with-jsondir=/path/to/jsondir) to manually specify a particular JSON-C installation directory that PostGISwill build against.

--with-gui Compile the data import GUI (requires GTK+2.0). This will create shp2pgsql-gui graphical interface to shp2pgsql.

--with-raster Compile with raster support. This will build rtpostgis-2.0.2 library and rtpostgis.sql file. This may not be requiredin final release as plan is to build in raster support by default.

--with-topology Compile with topology support. This will build the topology.sql file. There is no corresponding library as alllogic needed for topology is in postgis-2.0.2 library.

--with-gettext=no By default PostGIS will try to detect gettext support and compile with it, however if you run into incompatibil-ity issues that cause breakage of loader, you can disable it entirely with this command. Refer to ticket http://trac.osgeo.org/-postgis/ticket/748 for an example issue solved by configuring with this. NOTE: that you aren’t missing much by turningthis off. This is used for international help/label support for the GUI loader which is not yet documented and still experi-mental.

NoteIf you obtained PostGIS from the SVN repository , the first step is really to run the script./autogen.shThis script will generate the configure script that in turn is used to customize the installation of PostGIS.If you instead obtained PostGIS as a tarball, running ./autogen.sh is not necessary as configure has already beengenerated.

http://trac.osgeo.org/postgis/ticket/635

http://oss.metaparadigm.com/json-c/



http://svn.osgeo.org/postgis/trunk/


2.4.2 Building

Once the Makefile has been generated, building PostGIS is as simple as running

make

The last line of the output should be "PostGIS was built successfully. Ready to install."

As of PostGIS v1.4.0, all the functions have comments generated from the documentation. If you wish to install these commentsinto your spatial databases later, run the command which requires docbook. The postgis_comments.sql and other packagecomments files raster_comments.sql, topology_comments.sql are also packaged in the tar.gz distribution in the doc folder so noneed to make comments if installing from the tar ball.

make comments

Introduced in PostGIS 2.0. This generates html cheat sheets suitable for quick reference or for student handouts. This requiresxsltproc to build and will generate 4 files in doc folder topology_cheatsheet.html, tiger_geocoder_cheatsheet.html, raster_cheatsheet.html, postgis_cheatsheet.html

You can download some pre-built ones available in html and pdf from PostGIS / PostgreSQL Study Guides

make cheatsheets

2.4.3 Building PostGIS Extensions and Deploying them

The PostGIS extensions are built and installed automatically if you are using PostgreSQL 9.1+.

If you are building from source repository, you need to build the function descriptions first. These get built if you have docbookinstalled. You can also manually build with the statement:

make comments

Building the comments is not necessary if you are building from a release tar ball since these are packaged pre-built with the tarball already.

If you are building against PostgreSQL 9.1, the extensions should automatically build as part of the make install process. Youcan if needed build from the extensions folders or copy files if you need them on a different server.

cd extensionscd postgismake cleanmakemake installcd ..cd postgis_topologymake cleanmakemake install

The extension files will always be the same for the same version of PostGIS regardless of OS, so it is fine to copy over theextension files from one OS to another as long as you have the PostGIS binaries already installed on your servers.

If you want to install the extensions manually on a separate server different from your development, You need to copy thefollowing files from the extensions folder into the PostgreSQL / share / extension folder of your PostgreSQL installas well as the needed binaries for regular PostGIS if you don’t have them already on the server.

• These are the control files that denote information such as the version of the extension to install if not specified. postgis.control, postgis_topology.control.

• All the files in the /sql folder of each extension. Note that these need to be copied to the root of the PostgreSQL share/extensionfolder extensions/postgis/sql/*.sql, extensions/postgis_topology/sql/*.sql

http://www.postgis.us/study_guides


Once you do that, you should see postgis, postgis_topology as available extensions in PgAdmin -> extensions.

If you are using psql, you can verify that the extensions are installed by running this query:

SELECT name, default_version,installed_versionFROM pg_available_extensions WHERE name LIKE ’postgis%’ ;

name | default_version | installed_version-----------------+-----------------+-------------------postgis | 2.0.2 | 2.0.2postgis_topology | 2.0.2 |

If you have the extension installed in the database you are querying, you’ll see mention in the installed_version column.If you get no records back, it means you don’t have postgis extensions installed on the server at all. PgAdmin III 1.14+ will alsoprovide this information in the extensions section of the database browser tree and will even allow upgrade or uninstall byright-clicking.

If you have the extensions available, you can install postgis extension in your database of choice by either using pgAdminextension interface or running these sql commands:

CREATE EXTENSION postgis;CREATE EXTENSION postgis_topology;

WarningExtension tables spatial_ref_sys, layer, topology can not be explicitly backed up. They can only be backedup when the respective postgis or postgis_topology extension is backed up, which only seems to happenwhen you backup the whole database. As of PostGIS 2.0.1, only srid records not packaged with PostGIS are backedup when the database is backed up so don’t go around changing srids we package and expect your changes to bethere. Put in a ticket if you find an issue. The structures of extension tables are never backed up since they are createdwith CREATE EXTENSION and assumed to be the same for a given version of an extension. These behaviors arebuilt into the current PostgreSQL extension model, so nothing we can do about it.

If you installed 2.0.2, without using our wonderful extension system, you can change it to be extension based by first upgradingto the latest micro version running the upgrade scripts: postgis_upgrade_20_minor.sql,raster_upgrade_20_minor.sql,topology_upgrade_20_minor.sql.

If you installed postgis without raster support, you’ll need to install raster support first (using the full rtpostgis.sql

Then you can run teh below commands to package the functions in their respective extension.

CREATE EXTENSION postgis FROM unpackaged;CREATE EXTENSION postgis_topology FROM unpackaged;

2.4.4 Testing

If you wish to test the PostGIS build, run

make check

The above command will run through various checks and regression tests using the generated library against an actual Post-greSQL database.

NoteIf you configured PostGIS using non-standard PostgreSQL, GEOS, or Proj4 locations, you may need to add their librarylocations to the LD_LIBRARY_PATH environment variable.


CautionCurrently, the make check relies on the PATH and PGPORT environment variables when performing the checks - itdoes not use the PostgreSQL version that may have been specified using the configuration parameter --with-pgconfig.So make sure to modify your PATH to match the detected PostgreSQL installation during configuration or be preparedto deal with the impending headaches.

If successful, the output of the test should be similar to the following:

CUnit - A Unit testing framework for C - Version 2.1-0http://cunit.sourceforge.net/

Suite: print_suiteTest: test_lwprint_default_format ... passedTest: test_lwprint_format_orders ... passedTest: test_lwprint_optional_format ... passedTest: test_lwprint_oddball_formats ... passedTest: test_lwprint_bad_formats ... passed

Suite: Misc SuiteTest: test_misc_force_2d ... passedTest: test_misc_simplify ... passedTest: test_misc_count_vertices ... passedTest: test_misc_area ... passedTest: test_misc_wkb ... passed

Suite: PointArray SuiteTest: test_ptarray_append_point ... passedTest: test_ptarray_append_ptarray ... passed

Suite: PostGIS Computational Geometry SuiteTest: test_lw_segment_side ... passedTest: test_lw_segment_intersects ... passedTest: test_lwline_crossing_short_lines ... passedTest: test_lwline_crossing_long_lines ... passedTest: test_lwline_crossing_bugs ... passedTest: test_lwpoint_set_ordinate ... passedTest: test_lwpoint_get_ordinate ... passedTest: test_point_interpolate ... passedTest: test_lwline_clip ... passedTest: test_lwline_clip_big ... passedTest: test_lwmline_clip ... passedTest: test_geohash_point ... passedTest: test_geohash_precision ... passedTest: test_geohash ... passedTest: test_isclosed ... passed

Suite: PostGIS Measures SuiteTest: test_mindistance2d_tolerance ... passedTest: test_rect_tree_contains_point ... passedTest: test_rect_tree_intersects_tree ... passedTest: test_lwgeom_segmentize2d ... passed

Suite: WKT Out SuiteTest: test_wkt_out_point ... passedTest: test_wkt_out_linestring ... passedTest: test_wkt_out_polygon ... passedTest: test_wkt_out_multipoint ... passedTest: test_wkt_out_multilinestring ... passed

::--Run Summary: Type Total Ran Passed Failed

suites 17 17 n/a 0tests 143 143 143 0asserts 1228 1228 1228 0


Creating spatial db postgis_regPostgis 2.0.0SVN - 2011-01-11 15:33:37GEOS: 3.3.0-CAPI-1.7.0PROJ: Rel. 4.6.1, 21 August 2008

Running tests

loader/Point.............. okloader/PointM.............. okloader/PointZ.............. okloader/MultiPoint.............. okloader/MultiPointM.............. okloader/MultiPointZ.............. okloader/Arc.............. okloader/ArcM.............. okloader/ArcZ.......... okloader/Polygon.............. okloader/PolygonM.............. okloader/PolygonZ.............. okregress. okregress_index. okregress_index_nulls. oklwgeom_regress. okregress_lrs. okremovepoint. oksetpoint. oksimplify. oksnaptogrid. okaffine. okmeasures. oklong_xact. okctors. oksql-mm-serialize. oksql-mm-circularstring. oksql-mm-compoundcurve. oksql-mm-curvepoly. oksql-mm-general. oksql-mm-multicurve. oksql-mm-multisurface. okpolyhedralsurface. okout_geometry. okout_geography. okin_gml. okin_kml. okiscollection. okregress_ogc. okregress_ogc_cover. okregress_ogc_prep. okregress_bdpoly. okregress_proj. okdump. okdumppoints. okwmsservers_new. oktickets. okremove_repeated_points. oksplit. okrelatematch. okregress_buffer_params. okhausdorff. okclean. ok


sharedpaths. oksnap. ok

Run tests: 55Failed: 0

2.4.5 Installation

To install PostGIS, type

make install

This will copy the PostGIS installation files into their appropriate subdirectory specified by the --prefix configuration parameter.In particular:

• The loader and dumper binaries are installed in [prefix]/bin.

• The SQL files, such as postgis.sql, are installed in [prefix]/share/contrib.

• The PostGIS libraries are installed in [prefix]/lib.

If you previously ran the make comments command to generate the postgis_comments.sql, raster_comments.sqlfile, install the sql file by running

make comments-install

Notepostgis_comments.sql, raster_comments.sql, topology_comments.sql was separated from thetypical build and installation targets since with it comes the extra dependency of xsltproc.

2.5 Create a spatially-enabled database on PostgreSQL lower than 9.1

The first step in creating a PostGIS database is to create a simple PostgreSQL database.

createdb [yourdatabase]

Many of the PostGIS functions are written in the PL/pgSQL procedural language. As such, the next step to create a PostGISdatabase is to enable the PL/pgSQL language in your new database. This is accomplish by the command below command. ForPostgreSQL 8.4+, this is generally already installed

createlang plpgsql [yourdatabase]

Now load the PostGIS object and function definitions into your database by loading the postgis.sql definitions file (locatedin [prefix]/share/contrib as specified during the configuration step).

psql -d [yourdatabase] -f postgis.sql

For a complete set of EPSG coordinate system definition identifiers, you can also load the spatial_ref_sys.sql definitionsfile and populate the spatial_ref_sys table. This will permit you to perform ST_Transform() operations on geometries.

psql -d [yourdatabase] -f spatial_ref_sys.sql

If you wish to add comments to the PostGIS functions, the final step is to load the postgis_comments.sql into your spatialdatabase. The comments can be viewed by simply typing \dd [function_name] from a psql terminal window.

psql -d [yourdatabase] -f postgis_comments.sql

Install raster support

psql -d [yourdatabase] -f rtpostgis.sql


Install raster support comments. This will provide quick help info for each raster function using psql or PgAdmin or any otherPostgreSQL tool that can show function comments

psql -d [yourdatabase] -f raster_comments.sql

Install topology support

psql -d [yourdatabase] -f topology/topology.sql

Install topology support comments. This will provide quick help info for each topology function / type using psql or PgAdminor any other PostgreSQL tool that can show function comments

psql -d [yourdatabase] -f topology/topology_comments.sql

If you plan to restore an old backup from prior versions in this new db, run:

psql -d [yourdatabase] -f legacy.sql

NoteThere is an alternative legacy_minimal.sql you can run instead which will install barebones needed to recovertables and work with apps like MapServer and GeoServer. If you have views that use things like distance / length etc,you’ll need the full blown legacy.sql

You can later run uninstall_legacy.sql to get rid of the deprecated functions after you are done with restoring andcleanup.

2.6 Creating a spatial database using EXTENSIONS

If you are using PostgreSQL 9.1+ and have compiled and installed the extensions/ postgis modules, you can create a spatialdatabase the new way.

createdb [yourdatabase]

The core postgis extension installs PostGIS geometry, geography, raster, spatial_ref_sys and all the functions and comments witha simple:

CREATE EXTENSION postgis;

command.

psql -d [yourdatabase] -c "CREATE EXTENSION postgis;"

Topology is packaged as a separate extension and installable with command:

psql -d [yourdatabase] -c "CREATE EXTENSION postgis_topology;"

If you plan to restore an old backup from prior versions in this new db, run:

psql -d [yourdatabase] -f legacy.sql

You can later run uninstall_legacy.sql to get rid of the deprecated functions after you are done with restoring andcleanup.

2.7 Installing, Upgrading Tiger Geocoder and loading data

The Tiger geocoder does not get installed / upgraded with the core PostGIS scripts because it is only of regional use. In fact noth-ing located in the extras folder is installed by default with the regular PostGIS install / upgrade. Extras like Tiger geocoder mayalso not be packaged in your PostGIS distribution, but will always be available in the postgis-2.0.2.tar.gz file. The instructionsprovided here are also available in the extras/tiger_geocoder/tiger_2010/README

If you are on Windows and you don’t have tar installed, you can use http://www.7-zip.org/ to unzip the PostGIS tarball.

http://www.7-zip.org/


2.7.1 Tiger Geocoder Enabling your PostGIS database

First install PostGIS using the prior instructions.

If you don’t have an extras folder, download http://www.postgis.org/download/postgis-2.0.2.tar.gz

tar xvfz postgis-2.0.2.tar.gz

cd postgis-2.0.2/extras/tiger_geocoder/tiger_2010

Edit the tiger_loader.sql to the paths of your executables server etc.

If you are installing Tiger geocoder for the first time edit either the create_geocode.bat script If you are on windows or thecreate_geocode.sh if you are on Linux/Unix/Mac OSX with your PostgreSQL specific settings and run the correspondingscript from the commandline. If you don’t edit this file, it will just contain common case locations of items. You can edit thegenerated script after the fact when you run the Loader_Generate_Script command.

Verify that you now have a tiger schema in your database and that it is part of your database search_path. If it is not, add itwith a command something along the line of:

ALTER DATABASE geocoder SET search_path=public, tiger;

The normalizing address functionality works more or less without any data except for tricky addresses. Run this test and verifythings look like this:

SELECT pprint_addy(normalize_address(’202 East Fremont Street, Las Vegas, Nevada 89101’)) ←↩As pretty_address;

pretty_address---------------------------------------202 E Fremont St, Las Vegas, NV 89101

2.7.2 Upgrading your Tiger Geocoder Install

If you have Tiger Geocoder packaged with 2.0 already installed, you can upgrade the functions at any time even from an interimtar ball if there are fixes you badly need.

If you don’t have an extras folder, download http://www.postgis.org/download/postgis-2.0.2.tar.gz

tar xvfz postgis-2.0.2.tar.gz

cd postgis-2.0.2/extras/tiger_geocoder/tiger_2010

Locate the upgrade_geocoder.bat script If you are on windows or the upgrade_geocoder.sh if you are on Linux/U-nix/Mac OSX. Edit the file to have your postgis database credientials and run then corresponding script from the commandline.

2.7.3 Loading Tiger Data

The instructions for loading data are available in a more detailed form in the extras/tiger_geocoder/tiger_2010/README. This just includes the general steps.

The load process downloads data from the census website for the respective states requested, extracts the files, and thenloads each state into its own separate set of state tables. Each state table inherits from the tables defined in tiger schemaso that its sufficient to just query those tables to access all the data and drop a set of state tables at any time using theDrop_State_Tables_Generate_Script if you need to reload a state or just don’t need a state anymore.

In order to be able to load data you’ll need the following tools:

• A tool to unzip the zip files from census website.

For Unix like systems: unzip executable which is usually already installed on most Unix like platforms.

For Windows, 7-zip which is a free compress/uncompress tool you can download from http://www.7-zip.org/



http://www.7-zip.org/


• shp2pgsql commandline which is installed by default when you install PostGIS.

• wget which is a web grabber tool usually installed on most Unix/Linux systems.

If you are on windows, you can get pre-compiled binaries from http://gnuwin32.sourceforge.net/packages/wget.htm

To load data refer to Loader_Generate_Script to generate a data load script for your platform for the states you desire. Note thatyou can install these piecemeal. You don’t have to load all the states you want all at once. You can load them as you need them.

After the states you desire have been loaded, make sure to run the:

SELECT install_missing_indexes();

as described in Install_Missing_Indexes.

To test that things are working as they should, try to run a geocode on an address in your state using Geocode

2.8 Create a spatially-enabled database from a template

Some packaged distributions of PostGIS (in particular the Win32 installers for PostGIS >= 1.1.5) load the PostGIS functionsinto a template database called template_postgis. If the template_postgis database exists in your PostgreSQLinstallation then it is possible for users and/or applications to create spatially-enabled databases using a single command. Notethat in both cases, the database user must have been granted the privilege to create new databases.

From the shell:

# createdb -T template_postgis my_spatial_db

From SQL:

postgres=# CREATE DATABASE my_spatial_db TEMPLATE=template_postgis

2.9 Upgrading

Upgrading existing spatial databases can be tricky as it requires replacement or introduction of new PostGIS object definitions.

Unfortunately not all definitions can be easily replaced in a live database, so sometimes your best bet is a dump/reload process.

PostGIS provides a SOFT UPGRADE procedure for minor or bugfix releases, and a HARD UPGRADE procedure for majorreleases.

Before attempting to upgrade PostGIS, it is always worth to backup your data. If you use the -Fc flag to pg_dump you willalways be able to restore the dump with a HARD UPGRADE.

2.9.1 Soft upgrade

If you installed your database using extensions, you’ll need to upgrade using the extension model as well. If you installed usingthe old sql script way, then you should upgrade using the sql script way. Please refer to the appropriate.

2.9.1.1 Soft Upgrade Pre 9.1+ or without extensions

This section applies only to those who installed PostGIS not using extensions. If you have extensions and try to upgrade withthis approach you’ll get messages like:

can’t drop ... because postgis extension depends on it

http://gnuwin32.sourceforge.net/packages/wget.htm


After compiling you should find several postgis_upgrade*.sql files. Install the one for your version of PostGIS. Forexample postgis_upgrade_13_to_15.sql should be used if you are upgrading from PostGIS 1.3 to 1.5. If you aremoving from PostGIS 1.* to PostGIS 2.* or from PostGIS 2.* prior to r7409, you need to do a HARD UPGRADE.

psql -f postgis_upgrade_20_minor.sql -d your_spatial_database

The same procedure applies to raster and topology extensions, with upgrade files named rtpostgis_upgrade*.sql andtopology_upgrade*.sql respectively. If you need them:

psql -f rtpostgis_upgrade_20_minor.sql -d your_spatial_database

psql -f topology_upgrade_20_minor.sql -d your_spatial_database

NoteIf you can’t find the postgis_upgrade*.sql specific for upgrading your version you are using a version too earlyfor a soft upgrade and need to do a HARD UPGRADE.

The PostGIS_Full_Version function should inform you about the need to run this kind of upgrade using a "procs need upgrade"message.

2.9.1.2 Soft Upgrade 9.1+ using extensions

If you originally installed PostGIS with extensions, then you need to upgrade using extensions as well. Doing a minor upgradewith extensions, is fairly painless.

ALTER EXTENSION postgis UPDATE TO "2.0.2";ALTER EXTENSION postgis_topology UPDATE TO "2.0.2";

If you get an error notice something like:

No migration path defined for ... to 2.0.2

Then you’ll need to backup your database, create a fresh one as described in Section 2.6 and then restore your backup on top ofthis new database. You might get a message that postgis extension already installed which you can safely ignore.

NoteIf you installed PostGIS originally without a version specified, you can often skip the reinstallation of postgis extensionbefore restoring since the backup just has CREATE EXTENSION postgis and thus picks up the newest latestversion during restore. .

2.9.2 Hard upgrade

By HARD UPGRADE we mean full dump/reload of postgis-enabled databases. You need a HARD UPGRADE when PostGISobjects’ internal storage changes or when SOFT UPGRADE is not possible. The Release Notes appendix reports for each versionwhether you need a dump/reload (HARD UPGRADE) to upgrade.

The dump/reload process is assisted by the postgis_restore.pl script which takes care of skipping from the dump all definitionswhich belong to PostGIS (including old ones), allowing you to restore your schemas and data into a database with PostGISinstalled without getting duplicate symbol errors or bringing forward deprecated objects.

Supplementary instructions for windows users are available at Windows Hard upgrade.

The Procedure is as follows:

http://trac.osgeo.org/postgis/wiki/UsersWikiWinUpgrade


1. Create a "custom-format" dump of the database you want to upgrade (let’s call it olddb) include binary blobs (-b) andverbose (-v) output. The user can be the owner of the db, need not be postgres super account.

pg_dump -h localhost -p 5432 -U postgres -Fc -b -v -f "/somepath/olddb.backup" olddb

2. Do a fresh install of PostGIS in a new database -- we’ll refer to this database as newdb. Please refer to Section 2.5 andSection 2.6 for instructions on how to do this.

The spatial_ref_sys entries found in your dump will be restored, but they will not override existing ones in spatial_ref_sys.This is to ensure that fixes in the official set will be properly propagated to restored databases. If for any reason you reallywant your own overrides of standard entries just don’t load the spatial_ref_sys.sql file when creating the new db.

If your database is really old or you know you’ve been using long deprecated functions in your views and functions, youmight need to load legacy.sql for all your functions and views etc. to properly come back. Only do this if _really_needed. Consider upgrading your views and functions before dumping instead, if possible. The deprecated functions canbe later removed by loading uninstall_legacy.sql.

3. Restore your backup into your fresh newdb database using postgis_restore.pl. Unexpected errors, if any, will be printedto the standard error stream by psql. Keep a log of those.

perl utils/postgis_restore.pl "/somepath/olddb.backup" | psql -h localhost -p 5432 -U ←↩postgres newdb 2> errors.txt

Errors may arise in the following cases:

1. Some of your views or functions make use of deprecated PostGIS objects. In order to fix this you may try loadinglegacy.sql script prior to restore or you’ll have to restore to a version of PostGIS which still contains those objectsand try a migration again after porting your code. If the legacy.sql way works for you, don’t forget to fix your code tostop using deprecated functions and drop them loading uninstall_legacy.sql.

2. Some custom records of spatial_ref_sys in dump file have an invalid SRID value. Valid SRID values are bigger than 0 andsmaller than 999000. Values in the 999000.999999 range are reserved for internal use while values > 999999 can’t be usedat all. All your custom records with invalid SRIDs will be retained, with those > 999999 moved into the reserved range,but the spatial_ref_sys table would loose a check constraint guarding for that invariant to hold and possibly also its primarykey ( when multiple invalid SRIDS get converted to the same reserved SRID value ).

In order to fix this you should copy your custom SRS to a SRID with a valid value (maybe in the 910000..910999 range),convert all your tables to the new srid (see UpdateGeometrySRID), delete the invalid entry from spatial_ref_sys and re-construct the check(s) with:

ALTER TABLE spatial_ref_sys ADD CONSTRAINT spatial_ref_sys_srid_check check (srid > 0 ←↩AND srid < 999000 );

ALTER TABLE spatial_ref_sys ADD PRIMARY KEY(srid));

2.10 Common Problems

There are several things to check when your installation or upgrade doesn’t go as you expected.

1. Check that you have installed PostgreSQL 8.4 or newer, and that you are compiling against the same version of thePostgreSQL source as the version of PostgreSQL that is running. Mix-ups can occur when your (Linux) distribution hasalready installed PostgreSQL, or you have otherwise installed PostgreSQL before and forgotten about it. PostGIS will onlywork with PostgreSQL 8.4 or newer, and strange, unexpected error messages will result if you use an older version. Tocheck the version of PostgreSQL which is running, connect to the database using psql and run this query:

SELECT version();


If you are running an RPM based distribution, you can check for the existence of pre-installed packages using the rpmcommand as follows: rpm -qa | grep postgresql

2. If your upgrade fails, make sure you are restoring into a database that already has PostGIS installed.

SELECT postgis_full_version();

Also check that configure has correctly detected the location and version of PostgreSQL, the Proj4 library and the GEOS library.

1. The output from configure is used to generate the postgis_config.h file. Check that the POSTGIS_PGSQL_VER-SION, POSTGIS_PROJ_VERSION and POSTGIS_GEOS_VERSION variables have been set correctly.

2.11 JDBC

The JDBC extensions provide Java objects corresponding to the internal PostGIS types. These objects can be used to write Javaclients which query the PostGIS database and draw or do calculations on the GIS data in PostGIS.

1. Enter the java/jdbc sub-directory of the PostGIS distribution.

2. Run the ant command. Copy the postgis.jar file to wherever you keep your java libraries.

The JDBC extensions require a PostgreSQL JDBC driver to be present in the current CLASSPATH during the build process. Ifthe PostgreSQL JDBC driver is located elsewhere, you may pass the location of the JDBC driver JAR separately using the -Dparameter like this:

# ant -Dclasspath=/path/to/postgresql-jdbc.jar

PostgreSQL JDBC drivers can be downloaded from http://jdbc.postgresql.org .

2.12 Loader/Dumper

The data loader and dumper are built and installed automatically as part of the PostGIS build. To build and install them manually:

# cd postgis-2.0.2/loader# make# make install

The loader is called shp2pgsql and converts ESRI Shape files into SQL suitable for loading in PostGIS/PostgreSQL. Thedumper is called pgsql2shp and converts PostGIS tables (or queries) into ESRI Shape files. For more verbose documentation,see the online help, and the manual pages.

http://jdbc.postgresql.org


Chapter 3

PostGIS Frequently Asked Questions

1. My applications and desktop tools worked with PostGIS 1.5,but they don’t work with PostGIS 2.0. How do I fix this?

A lot of deprecated functions were removed from the PostGIS code base in PostGIS 2.0. This has affected applicationsin addition to third-party tools such as Geoserver, MapServer, QuantumGIS, and OpenJump to name a few. There are acouple of ways to resolve this. For the third-party apps, you can try to upgrade to the latest versions of these which havemany of these issues fixed. For your own code, you can change your code to not use the functions removed. Most of thesefunctions are non ST_ aliases of ST_Union, ST_Length etc. and as a last resort, install the whole of legacy.sql orjust the portions of legacy.sql you need.The legacy.sql file is located in the same folder as postgis.sql. You caninstall this file after you have installed postgis.sql and spatial_ref_sys.sql to get back all the 200 some-odd old functionswe removed.

2. When I load OpenStreetMap data with osm2pgsql, I’m getting an error failed: ERROR: operator class "gist_geometry_ops"does not exist for access method "gist" Error occurred. This worked fine in PostGIS 1.5.

In PostGIS 2, the default geometry operator class gist_geometry_ops was changed to gist_geometry_ops_2d and thegist_geometry_ops was completely removed. This was done because PostGIS 2 also introduced Nd spatial indexes for3D support and the old name was deemed confusing and a misnomer.Some older applications that as part of the processcreate tables and indexes, explicitly referenced the operator class name. This was unnecessary if you want the default 2Dindex. So if you manage said good, change index creation from:BAD:

CREATE INDEX idx_my_table_geom ON my_table USING gist(geom gist_geometry_ops);

To GOOD:

CREATE INDEX idx_my_table_geom ON my_table USING gist(geom);

The only case where you WILL need to specify the operator class is if you want a 3D spatial index as follows:

CREATE INDEX idx_my_super3d_geom ON my_super3d USING gist(geom gist_geometry_ops_nd);

If you are unfortunate to be stuck with compiled code you can’t change that has the old gist_geometry_ops hard-coded,then you can create the old class using the legacy_gist.sql packaged in PostGIS 2.0.2+. However if you use thisfix, you are advised to at a later point drop the index and recreate it without the operator class. This will save you grief inthe future when you need to upgrade again.

3. I’m running PostgreSQL 9.0 and I can no longer read/view geometries in OpenJump, Safe FME, and some other tools?

In PostgreSQL 9.0+, the default encoding for bytea data has been changed to hex and older JDBC drivers still assumeescape format. This has affected some applications such as Java applications using older JDBC drivers or .NET ap-plications that use the older npgsql driver that expect the old behavior of ST_AsBinary. There are two approaches togetting this to work again.You can upgrade your JDBC driver to the latest PostgreSQL 9.0 version which you can getfrom http://jdbc.postgresql.org/download.htmlIf you are running a .NET app, you can use Npgsql 2.0.11 or higher whichyou can download from http://pgfoundry.org/frs/?group_id=1000140 and as described on Francisco Figueiredo’s NpgSQL2.0.11 released blog entryIf upgrading your PostgreSQL driver is not an option, then you can set the default back to theold behavior with the following change:

http://jdbc.postgresql.org/download.html

http://pgfoundry.org/frs/?group_id=1000140

http://fxjr.blogspot.com/2010/11/npgsql-2011-released.html

http://fxjr.blogspot.com/2010/11/npgsql-2011-released.html


ALTER DATABASE mypostgisdb SET bytea_output=’escape’;

4. I tried to use PgAdmin to view my geometry column and it is blank, what gives?

PgAdmin doesn’t show anything for large geometries. The best ways to verify you do have data in your geometry columnsare?

-- this should return no records if all your geom fields are filled inSELECT somefield FROM mytable WHERE geom IS NULL;

-- To tell just how large your geometry is do a query of the form--which will tell you the most number of points you have in any of your geometry ←↩

columnsSELECT MAX(ST_NPoints(geom)) FROM sometable;

5. What kind of geometric objects can I store?

You can store point, line, polygon, multipoint, multiline, multipolygon, and geometrycollections. In PostGIS 2.0 and aboveyou can also store TINS and Polyhedral Surfaces in the basic geometry type. These are specified in the Open GIS WellKnown Text Format (with XYZ,XYM,XYZM extensions). There are three data types currently supported. The standardOGC geometry data type which uses a planar coordinate system for measurement, the geography data type which uses ageodetic coordinate system (not OGC, but you’ll find a similar type in Microsoft SQL Server 2008+). Only WGS 84 longlat (SRID:4326) is supported by the geography data type. The newest family member of the PostGIS spatial type familyis raster for storing and analyzing raster data. Raster has its very own FAQ. Refer to Chapter 10 and Chapter 9 for moredetails.

6. I’m all confused. Which data store should I use geometry or geography?

Short Answer: geography is a new data type that supports long range distances measurements, but most computations onit are currently slower than they are on geometry. If you use geography -- you don’t need to learn much about planarcoordinate systems. Geography is generally best if all you care about is measuring distances and lengths and you havedata from all over the world. Geometry data type is an older data type that has many more functions supporting it, enjoysgreater support from third party tools, and operations on it are generally faster -- sometimes as much as 10 fold fasterfor larger geometries. Geometry is best if you are pretty comfortable with spatial reference systems or you are dealingwith localized data where all your data fits in a single spatial reference system (SRID), or you need to do a lot of spatialprocessing. Note: It is fairly easy to do one-off conversions between the two types to gain the benefits of each. Refer toSection 13.10 to see what is currently supported and what is not. Long Answer: Refer to our more lengthy discussion inthe Section 4.2.2 and function type matrix.

7. I have more intense questions about geography, such as how big of a geographic region can I stuff in a geography columnand still get reasonable answers. Are there limitations such as poles, everything in the field must fit in a hemisphere (likeSQL Server 2008 has), speed etc?

Your questions are too deep and complex to be adequately answered in this section. Please refer to our Section 4.2.3.

8. How do I insert a GIS object into the database?

First, you need to create a table with a column of type "geometry" or "geography" to hold your GIS data. Storing geographytype data is a little different than storing geometry. Refer to Section 4.2.1 for details on storing geography. For geometry:Connect to your database with psql and try the following SQL:

CREATE TABLE gtest ( ID int4, NAME varchar(20) );SELECT AddGeometryColumn(’’, ’gtest’,’geom’,-1,’LINESTRING’,2);

If the geometry column addition fails, you probably have not loaded the PostGIS functions and objects into this database.See the Section 2.4.Then, you can insert a geometry into the table using a SQL insert statement. The GIS object itself isformatted using the OpenGIS Consortium "well-known text" format:

INSERT INTO gtest (ID, NAME, GEOM)VALUES (1,’First Geometry’,


ST_GeomFromText(’LINESTRING(2 3,4 5,6 5,7 8)’, -1));

For more information about other GIS objects, see the object reference.To view your GIS data in the table:

SELECT id, name, ST_AsText(geom) AS geom FROM gtest;

The return value should look something like this:

id | name | geom----+----------------+-----------------------------1 | First Geometry | LINESTRING(2 3,4 5,6 5,7 8)

(1 row)

9. How do I construct a spatial query?

The same way you construct any other database query, as an SQL combination of return values, functions, and booleantests.For spatial queries, there are two issues that are important to keep in mind while constructing your query: is there aspatial index you can make use of; and, are you doing expensive calculations on a large number of geometries.In general,you will want to use the "intersects operator" (&&) which tests whether the bounding boxes of features intersect. Thereason the && operator is useful is because if a spatial index is available to speed up the test, the && operator will makeuse of this. This can make queries much much faster.You will also make use of spatial functions, such as Distance(),ST_Intersects(), ST_Contains() and ST_Within(), among others, to narrow down the results of your search. Most spatialqueries include both an indexed test and a spatial function test. The index test serves to limit the number of return tuplesto only tuples that might meet the condition of interest. The spatial functions are then use to test the condition exactly.

SELECT id, the_geomFROM thetableWHEREST_Contains(the_geom,’POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))’);

10. How do I speed up spatial queries on large tables?

Fast queries on large tables is the raison d’etre of spatial databases (along with transaction support) so having a good indexis important.To build a spatial index on a table with a geometry column, use the "CREATE INDEX" function as follows:

CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );

The "USING GIST" option tells the server to use a GiST (Generalized Search Tree) index.

NoteGiST indexes are assumed to be lossy. Lossy indexes uses a proxy object (in the spatial case, a bounding box)for building the index.

You should also ensure that the PostgreSQL query planner has enough information about your index to make rationaldecisions about when to use it. To do this, you have to "gather statistics" on your geometry tables.For PostgreSQL8.0.x and greater, just run the VACUUM ANALYZE command.For PostgreSQL 7.4.x and below, run the SELECT UP-DATE_GEOMETRY_STATS() command.

11. Why aren’t PostgreSQL R-Tree indexes supported?

Early versions of PostGIS used the PostgreSQL R-Tree indexes. However, PostgreSQL R-Trees have been completelydiscarded since version 0.6, and spatial indexing is provided with an R-Tree-over-GiST scheme.Our tests have shownsearch speed for native R-Tree and GiST to be comparable. Native PostgreSQL R-Trees have two limitations which makethem undesirable for use with GIS features (note that these limitations are due to the current PostgreSQL native R-Treeimplementation, not the R-Tree concept in general):

• R-Tree indexes in PostgreSQL cannot handle features which are larger than 8K in size. GiST indexes can, using the"lossy" trick of substituting the bounding box for the feature itself.


• R-Tree indexes in PostgreSQL are not "null safe", so building an index on a geometry column which contains nullgeometries will fail.

12. Why should I use the AddGeometryColumn() function and all the other OpenGIS stuff?

If you do not want to use the OpenGIS support functions, you do not have to. Simply create tables as in older versions,defining your geometry columns in the CREATE statement. All your geometries will have SRIDs of -1, and the OpenGISmeta-data tables will not be filled in properly. However, this will cause most applications based on PostGIS to fail, and itis generally suggested that you do use AddGeometryColumn() to create geometry tables.MapServer is one applicationwhich makes use of the geometry_columns meta-data. Specifically, MapServer can use the SRID of the geometrycolumn to do on-the-fly reprojection of features into the correct map projection.

13. What is the best way to find all objects within a radius of another object?

To use the database most efficiently, it is best to do radius queries which combine the radius test with a bounding box test:the bounding box test uses the spatial index, giving fast access to a subset of data which the radius test is then applied to.TheST_DWithin(geometry, geometry, distance) function is a handy way of performing an indexed distancesearch. It works by creating a search rectangle large enough to enclose the distance radius, then performing an exactdistance search on the indexed subset of results.For example, to find all objects with 100 meters of POINT(1000 1000) thefollowing query would work well:

SELECT * FROM geotableWHERE ST_DWithin(geocolumn, ’POINT(1000 1000)’, 100.0);

14. How do I perform a coordinate reprojection as part of a query?

To perform a reprojection, both the source and destination coordinate systems must be defined in the SPATIAL_REF_SYStable, and the geometries being reprojected must already have an SRID set on them. Once that is done, a reprojection isas simple as referring to the desired destination SRID. The below projects a geometry to NAD 83 long lat. The below willonly work if the srid of the_geom is not -1 (not undefined spatial ref)

SELECT ST_Transform(the_geom,4269) FROM geotable;

15. I did an ST_AsEWKT and ST_AsText on my rather large geometry and it returned blank field. What gives?

You are probably using PgAdmin or some other tool that doesn’t output large text. If your geometry is big enough, it willappear blank in these tools. Use PSQL if you really need to see it or output it in WKT.

--To check number of geometries are really blankSELECT count(gid) FROM geotable WHERE the_geom IS NULL;

16. When I do an ST_Intersects, it says my two geometries don’t intersect when I KNOW THEY DO. What gives?

This generally happens in two common cases. Your geometry is invalid -- check ST_IsValid or you are assuming theyintersect because ST_AsText truncates the numbers and you have lots of decimals after it is not showing you.

17. I am releasing software that uses PostGIS, does that mean my software has to be licensed using the GPL like PostGIS?Will I have to publish all my code if I use PostGIS?

Almost certainly not. As an example, consider Oracle database running on Linux. Linux is GPL, Oracle is not, doesOracle running on Linux have to be distributed using the GPL? No. So your software can use a PostgreSQL/PostGISdatabase as much as it wants and be under any license you like.The only exception would be if you made changes to thePostGIS source code, and distributed your changed version of PostGIS. In that case you would have to share the code ofyour changed PostGIS (but not the code of applications running on top of it). Even in this limited case, you would stillonly have to distribute source code to people you distributed binaries to. The GPL does not require that you publish yoursource code, only that you share it with people you give binaries to.


Chapter 4

Using PostGIS: Data Management and Queries

4.1 GIS Objects

The GIS objects supported by PostGIS are a superset of the "Simple Features" defined by the OpenGIS Consortium (OGC). Asof version 0.9, PostGIS supports all the objects and functions specified in the OGC "Simple Features for SQL" specification.

PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates.

4.1.1 OpenGIS WKB and WKT

The OpenGIS specification defines two standard ways of expressing spatial objects: the Well-Known Text (WKT) form and theWell-Known Binary (WKB) form. Both WKT and WKB include information about the type of the object and the coordinateswhich form the object.

Examples of the text representations (WKT) of the spatial objects of the features are as follows:

• POINT(0 0)

• LINESTRING(0 0,1 1,1 2)

• POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))

• MULTIPOINT(0 0,1 2)

• MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4))

• MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

• GEOMETRYCOLLECTION(POINT(2 3),LINESTRING(2 3,3 4))

The OpenGIS specification also requires that the internal storage format of spatial objects include a spatial referencing systemidentifier (SRID). The SRID is required when creating spatial objects for insertion into the database.

Input/Output of these formats are available using the following interfaces:

bytea WKB = ST_AsBinary(geometry);text WKT = ST_AsText(geometry);geometry = ST_GeomFromWKB(bytea WKB, SRID);geometry = ST_GeometryFromText(text WKT, SRID);

For example, a valid insert statement to create and insert an OGC spatial object would be:

INSERT INTO geotable ( the_geom, the_name )VALUES ( ST_GeomFromText(’POINT(-126.4 45.32)’, 312), ’A Place’);


4.1.2 PostGIS EWKB, EWKT and Canonical Forms

OGC formats only support 2d geometries, and the associated SRID is *never* embedded in the input/output representations.

PostGIS extended formats are currently superset of OGC one (every valid WKB/WKT is a valid EWKB/EWKT) but this mightvary in the future, specifically if OGC comes out with a new format conflicting with our extensions. Thus you SHOULD NOTrely on this feature!

PostGIS EWKB/EWKT add 3dm,3dz,4d coordinates support and embedded SRID information.

Examples of the text representations (EWKT) of the extended spatial objects of the features are as follows. The * ones are newin this version of PostGIS:

• POINT(0 0 0) -- XYZ

• SRID=32632;POINT(0 0) -- XY with SRID

• POINTM(0 0 0) -- XYM

• POINT(0 0 0 0) -- XYZM

• SRID=4326;MULTIPOINTM(0 0 0,1 2 1) -- XYM with SRID

• MULTILINESTRING((0 0 0,1 1 0,1 2 1),(2 3 1,3 2 1,5 4 1))

• POLYGON((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

• MULTIPOLYGON(((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)),((-1 -1 0,-1 -2 0,-2 -2 0,-2 -1 0,-1 -1 0)))

• GEOMETRYCOLLECTIONM( POINTM(2 3 9), LINESTRINGM(2 3 4, 3 4 5) )

• MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4) )

• POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 00 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

• TRIANGLE ((0 0, 0 9, 9 0, 0 0))

• TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

Input/Output of these formats are available using the following interfaces:

bytea EWKB = ST_AsEWKB(geometry);text EWKT = ST_AsEWKT(geometry);geometry = ST_GeomFromEWKB(bytea EWKB);geometry = ST_GeomFromEWKT(text EWKT);

For example, a valid insert statement to create and insert a PostGIS spatial object would be:

INSERT INTO geotable ( the_geom, the_name )VALUES ( ST_GeomFromEWKT(’SRID=312;POINTM(-126.4 45.32 15)’), ’A Place’ )

The "canonical forms" of a PostgreSQL type are the representations you get with a simple query (without any function call) andthe one which is guaranteed to be accepted with a simple insert, update or copy. For the postgis ’geometry’ type these are:

- Output- binary: EWKBascii: HEXEWKB (EWKB in hex form)

- Input- binary: EWKBascii: HEXEWKB|EWKT

For example this statement reads EWKT and returns HEXEWKB in the process of canonical ascii input/output:


=# SELECT ’SRID=4;POINT(0 0)’::geometry;

geometry----------------------------------------------------01010000200400000000000000000000000000000000000000(1 row)

4.1.3 SQL-MM Part 3

The SQL Multimedia Applications Spatial specification extends the simple features for SQL spec by defining a number ofcircularly interpolated curves.

The SQL-MM definitions include 3dm, 3dz and 4d coordinates, but do not allow the embedding of SRID information.

The well-known text extensions are not yet fully supported. Examples of some simple curved geometries are shown below:

• CIRCULARSTRING(0 0, 1 1, 1 0)

CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0)

The CIRCULARSTRING is the basic curve type, similar to a LINESTRING in the linear world. A single segment requiredthree points, the start and end points (first and third) and any other point on the arc. The exception to this is for a closed circle,where the start and end points are the same. In this case the second point MUST be the center of the arc, ie the oppositeside of the circle. To chain arcs together, the last point of the previous arc becomes the first point of the next arc, just like inLINESTRING. This means that a valid circular string must have an odd number of points greated than 1.

• COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))

A compound curve is a single, continuous curve that has both curved (circular) segments and linear segments. That means thatin addition to having well-formed components, the end point of every component (except the last) must be coincident with thestart point of the following component.

• CURVEPOLYGON(CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),(1 1, 3 3, 3 1, 1 1))

Example compound curve in a curve polygon: CURVEPOLYGON(COMPOUNDCURVE(CIRCULARSTRING(0 0,2 0, 2 1,2 3, 4 3),(4 3, 4 5, 1 4, 0 0)), CIRCULARSTRING(1.7 1, 1.4 0.4, 1.6 0.4, 1.6 0.5, 1.7 1) )

A CURVEPOLYGON is just like a polygon, with an outer ring and zero or more inner rings. The difference is that a ring cantake the form of a circular string, linear string or compound string.

As of PostGIS 1.4 PostGIS supports compound curves in a curve polygon.

• MULTICURVE((0 0, 5 5),CIRCULARSTRING(4 0, 4 4, 8 4))

The MULTICURVE is a collection of curves, which can include linear strings, circular strings or compound strings.

• MULTISURFACE(CURVEPOLYGON(CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),(1 1, 3 3, 3 1, 1 1)),((10 10, 14 12, 11 10,10 10),(11 11, 11.5 11, 11 11.5, 11 11)))

This is a collection of surfaces, which can be (linear) polygons or curve polygons.

NotePostGIS prior to 1.4 does not support compound curves in a curve polygon, but PostGIS 1.4 and above do support theuse of Compound Curves in a Curve Polygon.

NoteAll floating point comparisons within the SQL-MM implementation are performed to a specified tolerance, currently1E-8.


4.2 PostGIS Geography Type

The geography type provides native support for spatial features represented on "geographic" coordinates (sometimes called"geodetic" coordinates, or "lat/lon", or "lon/lat"). Geographic coordinates are spherical coordinates expressed in angular units(degrees).

The basis for the PostGIS geometry type is a plane. The shortest path between two points on the plane is a straight line. Thatmeans calculations on geometries (areas, distances, lengths, intersections, etc) can be calculated using cartesian mathematics andstraight line vectors.

The basis for the PostGIS geographic type is a sphere. The shortest path between two points on the sphere is a great circle arc.That means that calculations on geographies (areas, distances, lengths, intersections, etc) must be calculated on the sphere, usingmore complicated mathematics. For more accurate measurements, the calculations must take the actual spheroidal shape of theworld into account, and the mathematics becomes very complicated indeed.

Because the underlying mathematics is much more complicated, there are fewer functions defined for the geography type thanfor the geometry type. Over time, as new algorithms are added, the capabilities of the geography type will expand.

One restriction is that it only supports WGS 84 long lat (SRID:4326). It uses a new data type called geography. None of theGEOS functions support this new type. As a workaround one can convert back and forth between geometry and geography types.

The new geography type uses the PostgreSQL 8.3+ typmod definition format so that a table with a geography field can be addedin a single step. All the standard OGC formats except for curves are supported.

4.2.1 Geography Basics

The geography type only supports the simplest of simple features. Standard geometry type data will autocast to geography if itis of SRID 4326. You can also use the EWKT and EWKB conventions to insert data.

• POINT: Creating a table with 2d point geometry:

CREATE TABLE testgeog(gid serial PRIMARY KEY, the_geog geography(POINT,4326) );

Creating a table with z coordinate point

CREATE TABLE testgeog(gid serial PRIMARY KEY, the_geog geography(POINTZ,4326) );

• LINESTRING

• POLYGON

• MULTIPOINT

• MULTILINESTRING

• MULTIPOLYGON

• GEOMETRYCOLLECTION

The new geography fields don’t get registered in the geometry_columns. They get registered in a new view called ge-ography_columns which is a view against the system catalogs so is always automatically kept up to date without need for anAddGeom... like function.

Now, check the "geography_columns" view and see that your table is listed.

You can create a new table with a GEOGRAPHY column using the CREATE TABLE syntax. Unlike GEOMETRY, there is noneed to run a separate AddGeometryColumns() process to register the column in metadata.

CREATE TABLE global_points (id SERIAL PRIMARY KEY,name VARCHAR(64),location GEOGRAPHY(POINT,4326)

);


Note that the location column has type GEOGRAPHY and that geography type supports two optional modifier: a type modifierthat restricts the kind of shapes and dimensions allowed in the column; an SRID modifier that restricts the coordinate referenceidentifier to a particular number.

Allowable values for the type modifier are: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MUL-TIPOLYGON. The modifier also supports dimensionality restrictions through suffixes: Z, M and ZM. So, for example a modifierof ’LINESTRINGM’ would only allow line strings with three dimensions in, and would treat the third dimension as a measure.Similarly, ’POINTZM’ would expect four dimensional data.

The SRID modifier is currently of limited use: only 4326 (WGS84) is allowed as a value. If you do not specify an SRID, the avalue 0 (undefined spheroid) will be used, and all calculations will proceed using WGS84 anyways.

In the future, alternate SRIDs will allow calculations on spheroids other than WGS84.

Once you have created your table, you can see it in the GEOGRAPHY_COLUMNS table:

-- See the contents of the metadata viewSELECT * FROM geography_columns;

You can insert data into the table the same as you would if it was using a GEOMETRY column:

-- Add some data into the test tableINSERT INTO global_points (name, location) VALUES (’Town’, ST_GeographyFromText(’SRID=4326; ←↩

POINT(-110 30)’) );INSERT INTO global_points (name, location) VALUES (’Forest’, ST_GeographyFromText(’SRID ←↩

=4326;POINT(-109 29)’) );INSERT INTO global_points (name, location) VALUES (’London’, ST_GeographyFromText(’SRID ←↩

=4326;POINT(0 49)’) );

Creating an index works the same as GEOMETRY. PostGIS will note that the column type is GEOGRAPHY and create anappropriate sphere-based index instead of the usual planar index used for GEOMETRY.

-- Index the test table with a spherical indexCREATE INDEX global_points_gix ON global_points USING GIST ( location );

Query and measurement functions use units of meters. So distance parameters should be expressed in meters, and return valuesshould be expected in meters (or square meters for areas).

-- Show a distance query and note, London is outside the 1000km toleranceSELECT name FROM global_points WHERE ST_DWithin(location, ST_GeographyFromText(’SRID ←↩

=4326;POINT(-110 29)’), 1000000);

You can see the power of GEOGRAPHY in action by calculating the how close a plane flying from Seattle to London (LINESTRING(-122.33 47.606, 0.0 51.5)) comes to Reykjavik (POINT(-21.96 64.15)).

-- Distance calculation using GEOGRAPHY (122.2km)SELECT ST_Distance(’LINESTRING(-122.33 47.606, 0.0 51.5)’::geography, ’POINT(-21.96 ←↩

64.15)’:: geography);

-- Distance calculation using GEOMETRY (13.3 "degrees")SELECT ST_Distance(’LINESTRING(-122.33 47.606, 0.0 51.5)’::geometry, ’POINT(-21.96 64.15) ←↩

’:: geometry);

The GEOGRAPHY type calculates the true shortest distance over the sphere between Reykjavik and the great circle flight pathbetween Seattle and London.

Great Circle mapper The GEOMETRY type calculates a meaningless cartesian distance between Reykjavik and the straight linepath from Seattle to London plotted on a flat map of the world. The nominal units of the result might be called "degrees", but theresult doesn’t correspond to any true angular difference between the points, so even calling them "degrees" is inaccurate.

http://gc.kls2.com/cgi-bin/gc?PATH=SEA-LHR


4.2.2 When to use Geography Data type over Geometry data type

The new GEOGRAPHY type allows you to store data in longitude/latitude coordinates, but at a cost: there are fewer functionsdefined on GEOGRAPHY than there are on GEOMETRY; those functions that are defined take more CPU time to execute.

The type you choose should be conditioned on the expected working area of the application you are building. Will your dataspan the globe or a large continental area, or is it local to a state, county or municipality?

• If your data is contained in a small area, you might find that choosing an appropriate projection and using GEOMETRY is thebest solution, in terms of performance and functionality available.

• If your data is global or covers a continental region, you may find that GEOGRAPHY allows you to build a system withouthaving to worry about projection details. You store your data in longitude/latitude, and use the functions that have been definedon GEOGRAPHY.

• If you don’t understand projections, and you don’t want to learn about them, and you’re prepared to accept the limitations infunctionality available in GEOGRAPHY, then it might be easier for you to use GEOGRAPHY than GEOMETRY. Simply loadyour data up as longitude/latitude and go from there.

Refer to Section 13.10 for compare between what is supported for Geography vs. Geometry. For a brief listing and descriptionof Geography functions, refer to Section 13.3

4.2.3 Geography Advanced FAQ

1. Do you calculate on the sphere or the spheroid?

By default, all distance and area calculations are done on the spheroid. You should find that the results of calculations inlocal areas match up will with local planar results in good local projections. Over larger areas, the spheroidal calculationswill be more accurate than any calculation done on a projected plane. All the geography functions have the option ofusing a sphere calculation, by setting a final boolean parameter to ’FALSE’. This will somewhat speed up calculations,particularly for cases where the geometries are very simple.

2. What about the date-line and the poles?

All the calculations have no conception of date-line or poles, the coordinates are spherical (longitude/latitude) so a shapethat crosses the dateline is, from a calculation point of view, no different from any other shape.

3. What is the longest arc you can process?

We use great circle arcs as the "interpolation line" between two points. That means any two points are actually joined uptwo ways, depending on which direction you travel along the great circle. All our code assumes that the points are joinedby the *shorter* of the two paths along the great circle. As a consequence, shapes that have arcs of more than 180 degreeswill not be correctly modelled.

4. Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

Because the polygon is so darned huge! Big areas are bad for two reasons: their bounds are huge, so the index tends to pullthe feature no matter what query you run; the number of vertices is huge, and tests (distance, containment) have to traversethe vertex list at least once and sometimes N times (with N being the number of vertices in the other candidate feature).As with GEOMETRY, we recommend that when you have very large polygons, but are doing queries in small areas, you"denormalize" your geometric data into smaller chunks so that the index can effectively subquery parts of the object andso queries don’t have to pull out the whole object every time. Just because you *can* store all of Europe in one polygondoesn’t mean you *should*.

4.3 Using OpenGIS Standards

The OpenGIS "Simple Features Specification for SQL" defines standard GIS object types, the functions required to manipulatethem, and a set of meta-data tables. In order to ensure that meta-data remain consistent, operations such as creating and removinga spatial column are carried out through special procedures defined by OpenGIS.

There are two OpenGIS meta-data tables: SPATIAL_REF_SYS and GEOMETRY_COLUMNS. The SPATIAL_REF_SYS tableholds the numeric IDs and textual descriptions of coordinate systems used in the spatial database.


4.3.1 The SPATIAL_REF_SYS Table and Spatial Reference Systems

The spatial_ref_sys table is a PostGIS included and OGC compliant database table that lists over 3000 known spatial referencesystems and details needed to transform/reproject between them.

Although the PostGIS spatial_ref_sys table contains over 3000 of the more commonly used spatial reference system definitionsthat can be handled by the proj library, it does not contain all known to man and you can even define your own custom projectionif you are familiar with proj4 constructs. Keep in mind that most spatial reference systems are regional and have no meaningwhen used outside of the bounds they were intended for.

An excellent resource for finding spatial reference systems not defined in the core set is http://spatialreference.org/

Some of the more commonly used spatial reference systems are: 4326 - WGS 84 Long Lat, 4269 - NAD 83 Long Lat, 3395 -WGS 84 World Mercator, 2163 - US National Atlas Equal Area, Spatial reference systems for each NAD 83, WGS 84 UTMzone - UTM zones are one of the most ideal for measurement, but only cover 6-degree regions.

Various US state plane spatial reference systems (meter or feet based) - usually one or 2 exists per US state. Most of the meterones are in the core set, but many of the feet based ones or ESRI created ones you will need to pull from spatialreference.org.

For details on determining which UTM zone to use for your area of interest, check out the utmzone PostGIS plpgsql helperfunction.

The SPATIAL_REF_SYS table definition is as follows:

CREATE TABLE spatial_ref_sys (srid INTEGER NOT NULL PRIMARY KEY,auth_name VARCHAR(256),auth_srid INTEGER,srtext VARCHAR(2048),proj4text VARCHAR(2048)

)

The SPATIAL_REF_SYS columns are as follows:

SRID An integer value that uniquely identifies the Spatial Referencing System (SRS) within the database.

AUTH_NAME The name of the standard or standards body that is being cited for this reference system. For example, "EPSG"would be a valid AUTH_NAME.

AUTH_SRID The ID of the Spatial Reference System as defined by the Authority cited in the AUTH_NAME. In the case ofEPSG, this is where the EPSG projection code would go.

SRTEXT The Well-Known Text representation of the Spatial Reference System. An example of a WKT SRS representation is:

PROJCS["NAD83 / UTM Zone 10N",GEOGCS["NAD83",DATUM["North_American_Datum_1983",

SPHEROID["GRS 1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-123],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["metre",1]

]

For a listing of EPSG projection codes and their corresponding WKT representations, see http://www.opengeospatial.org/.For a discussion of WKT in general, see the OpenGIS "Coordinate Transformation Services Implementation Specification"at http://www.opengeospatial.org/standards. For information on the European Petroleum Survey Group (EPSG) and theirdatabase of spatial reference systems, see http://www.epsg.org.

http://www.sharpgis.net/post/2007/05/Spatial-references2c-coordinate-systems2c-projections2c-datums2c-ellipsoids-e28093-confusing.aspx

http://www.sharpgis.net/post/2007/05/Spatial-references2c-coordinate-systems2c-projections2c-datums2c-ellipsoids-e28093-confusing.aspx

http://spatialreference.org/

http://spatialreference.org/ref/epsg/4326/





http://spatialreference.org

http://trac.osgeo.org/postgis/wiki/UsersWikiplpgsqlfunctionsDistance

http://trac.osgeo.org/postgis/wiki/UsersWikiplpgsqlfunctionsDistance

http://en.wikipedia.org/wiki/SRID


http://www.opengeospatial.org/standards

http://www.epsg.org/


PROJ4TEXT PostGIS uses the Proj4 library to provide coordinate transformation capabilities. The PROJ4TEXT columncontains the Proj4 coordinate definition string for a particular SRID. For example:

+proj=utm +zone=10 +ellps=clrk66 +datum=NAD27 +units=m

For more information about, see the Proj4 web site at http://trac.osgeo.org/proj/. The spatial_ref_sys.sql filecontains both SRTEXT and PROJ4TEXT definitions for all EPSG projections.

4.3.2 The GEOMETRY_COLUMNS VIEW

In versions of PostGIS prior to 2.0.0, geometry_columns was a table that could be directly edited, and sometimes got out ofsynch with the actual definition of the geometry columns. In PostGIS 2.0.0, GEOMETRY_COLUMNS became a view with thesame front-facing structure as prior versions, but reading from database system catalogs Its structure is as follows:

\d geometry_columns

View "public.geometry_columns"Column | Type | Modifiers

-------------------+------------------------+-----------f_table_catalog | character varying(256) |f_table_schema | character varying(256) |f_table_name | character varying(256) |f_geometry_column | character varying(256) |coord_dimension | integer |srid | integer |type | character varying(30) |

The column meanings have not changed from prior versions and are:

F_TABLE_CATALOG, F_TABLE_SCHEMA, F_TABLE_NAME The fully qualified name of the feature table containingthe geometry column. Note that the terms "catalog" and "schema" are Oracle-ish. There is not PostgreSQL analogue of"catalog" so that column is left blank -- for "schema" the PostgreSQL schema name is used (public is the default).

F_GEOMETRY_COLUMN The name of the geometry column in the feature table.

COORD_DIMENSION The spatial dimension (2, 3 or 4 dimensional) of the column.

SRID The ID of the spatial reference system used for the coordinate geometry in this table. It is a foreign key reference to theSPATIAL_REF_SYS.

TYPE The type of the spatial object. To restrict the spatial column to a single type, use one of: POINT, LINESTRING, POLY-GON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION or corresponding XYMversions POINTM, LINESTRINGM, POLYGONM, MULTIPOINTM, MULTILINESTRINGM, MULTIPOLYGONM,GEOMETRYCOLLECTIONM. For heterogeneous (mixed-type) collections, you can use "GEOMETRY" as the type.

NoteThis attribute is (probably) not part of the OpenGIS specification, but is required for ensuring type homogeneity.

4.3.3 Creating a Spatial Table

Creating a table with spatial data, can be done in one step. As shown in the following example which creates a roads table witha 2D linestring geometry column in WGS84 long lat

CREATE TABLE ROADS ( ID int4, ROAD_NAME varchar(25), geom geometry(LINESTRING,4326) );



We can add additional columns using standard ALTER TABLE command as we do in this next example where we add a 3-Dlinestring.

ALTER TABLE roads ADD COLUMN geom2 geometry(LINESTRINGZ,4326);

For backwards compability, you can still create a spatial table in two stages using the management functions.

• Create a normal non-spatial table.

For example: CREATE TABLE ROADS ( ID int4, ROAD_NAME varchar(25) )

• Add a spatial column to the table using the OpenGIS "AddGeometryColumn" function. Refer to AddGeometryColumn formore details.

The syntax is:

AddGeometryColumn(<schema_name>,<table_name>,<column_name>,<srid>,<type>,<dimension>

)

Or, using current schema:

AddGeometryColumn(<table_name>,<column_name>,<srid>,<type>,<dimension>

)

Example1: SELECT AddGeometryColumn(’public’, ’roads’, ’geom’, 423, ’LINESTRING’, 2)Example2: SELECT AddGeometryColumn( ’roads’, ’geom’, 423, ’LINESTRING’, 2)

Here is an example of SQL used to create a table and add a spatial column (assuming that an SRID of 128 exists already):

CREATE TABLE parks (park_id INTEGER,park_name VARCHAR,park_date DATE,park_type VARCHAR

);SELECT AddGeometryColumn(’parks’, ’park_geom’, 128, ’MULTIPOLYGON’, 2 );

Here is another example, using the generic "geometry" type and the undefined SRID value of 0:

CREATE TABLE roads (road_id INTEGER,road_name VARCHAR

);SELECT AddGeometryColumn( ’roads’, ’roads_geom’, 0, ’GEOMETRY’, 3 );

4.3.4 Manually Registering Geometry Columns in geometry_columns

The AddGeometryColumn() approach creates a geometry column and also registers the new column in the geometry_columnstable. If your software utilizes geometry_columns, then any geometry columns you need to query by must be registered in thisview. Starting with PoastGIS 2.0, geometry_columns is no longer editable and all geometry columns are autoregistered.


However they may be registered as a generic geometry column if the column was not defined as a specific type during creation.

Two of the cases where this may happen, but you can’t use AddGeometryColumn, is in the case of SQL Views and bulk inserts.For these cases, you can correct the registration in the geometry_columns table by constraining the column. Note in PostGIS2.0+ if your column is typmod based, the creation process would register it correctly, so no need to do anything.

--Lets say you have a view created like thisCREATE VIEW public.vwmytablemercator AS

SELECT gid, ST_Transform(geom,3395) As geom, f_nameFROM public.mytable;

-- For it to register correctly in PostGIS 2.0+-- You need to cast the geometry--DROP VIEW public.vwmytablemercator;CREATE VIEW public.vwmytablemercator AS

SELECT gid, ST_Transform(geom,3395)::geometry(Geometry, 3395) As geom, f_nameFROM public.mytable;

-- If you know the geometry type for sure is a 2D POLYGON then you could doDROP VIEW public.vwmytablemercator;CREATE VIEW public.vwmytablemercator AS

SELECT gid, ST_Transform(geom,3395)::geometry(Polygon, 3395) As geom, f_nameFROM public.mytable;

--Lets say you created a derivative table by doing a bulk insertSELECT poi.gid, poi.geom, citybounds.city_nameINTO myschema.my_special_poisFROM poi INNER JOIN citybounds ON ST_Intersects(citybounds.geom, poi.geom);

--Create 2d index on new tableCREATE INDEX idx_myschema_myspecialpois_geom_gist

ON myschema.my_special_pois USING gist(geom);

-- If your points are 3D points or 3M points,-- then you might want to create an nd index instead of a 2d index-- like soCREATE INDEX my_special_pois_geom_gist_nd

ON my_special_pois USING gist(geom gist_geometry_ops_nd);

--To manually register this new table’s geometry column in geometry_columns-- Note that this approach will work for both PostGIS 2.0+ and PostGIS 1.4+-- For PostGIS 2.0 it will also change the underlying structure of the table to-- to make the column typmod based.-- For PostGIS prior to 2.0, this technique can also be used to register viewsSELECT populate_geometry_columns(’myschema.my_special_pois’::regclass);

--If you are using PostGIS 2.0 and for whatever reason, you-- you need the old constraint based definition behavior-- (such as case of inherited tables where all children do not have the same type and srid)-- set new optional use_typmod argument to falseSELECT populate_geometry_columns(’myschema.my_special_pois’::regclass, false);

Although the old-constraint based method is still supported, a constraint-based geomentry column used directly in a view, willnot register correctly in geometry_columns, as will a typmod one. In this example we define a column using typmod and anotherusing constraints.

CREATE TABLE pois_ny(gid SERIAL PRIMARY KEY, poi_name text, cat varchar(20), geom geometry(POINT,4326) );

SELECT AddGeometryColumn(’pois_ny’, ’geom_2160’, 2160, ’POINT’, 2, false);


If we run in psql

\d pois_ny;

We observe they are defined differently -- one is typmod, one is constraint

Table "public.pois_ny"Column | Type | Modifiers

-----------+-----------------------+------------------------------------------------------gid | integer | not null default nextval(’pois_ny_gid_seq’::regclass)poi_name | text |cat | character varying(20) |geom | geometry(Point,4326) |geom_2160 | geometry |

Indexes:"pois_ny_pkey" PRIMARY KEY, btree (gid)

Check constraints:"enforce_dims_geom_2160" CHECK (st_ndims(geom_2160) = 2)"enforce_geotype_geom_2160" CHECK (geometrytype(geom_2160) = ’POINT’::text

OR geom_2160 IS NULL)"enforce_srid_geom_2160" CHECK (st_srid(geom_2160) = 2160)

In geometry_columns, they both register correctly

SELECT f_table_name, f_geometry_column, srid, typeFROM geometry_columnsWHERE f_table_name = ’pois_ny’;

f_table_name | f_geometry_column | srid | type-------------+-------------------+------+-------pois_ny | geom | 4326 | POINTpois_ny | geom_2160 | 2160 | POINT

However -- if we were to create a view like this

CREATE VIEW vw_pois_ny_parks ASSELECT *

FROM pois_nyWHERE cat=’park’;

SELECT f_table_name, f_geometry_column, srid, typeFROM geometry_columnsWHERE f_table_name = ’vw_pois_ny_parks’;

The typmod based geom view column registers correctly, but the constraint based one does not.

f_table_name | f_geometry_column | srid | type------------------+-------------------+------+----------vw_pois_ny_parks | geom | 4326 | POINTvw_pois_ny_parks | geom_2160 | 0 | GEOMETRY

This may change in future versions of PostGIS, but for now To force the constraint based view column to register correctly, weneed to do this:

DROP VIEW vw_pois_ny_parks;CREATE VIEW vw_pois_ny_parks ASSELECT gid, poi_name, cat

, geom, geom_2160::geometry(POINT,2160) As geom_2160FROM pois_nyWHERE cat=’park’;


SELECT f_table_name, f_geometry_column, srid, typeFROM geometry_columnsWHERE f_table_name = ’vw_pois_ny_parks’;

f_table_name | f_geometry_column | srid | type------------------+-------------------+------+-------vw_pois_ny_parks | geom | 4326 | POINTvw_pois_ny_parks | geom_2160 | 2160 | POINT

4.3.5 Ensuring OpenGIS compliancy of geometries

PostGIS is compliant with the Open Geospatial Consortium’s (OGC) OpenGIS Specifications. As such, many PostGIS methodsrequire, or more accurately, assume that geometries that are operated on are both simple and valid. For example, it does notmake sense to calculate the area of a polygon that has a hole defined outside of the polygon, or to construct a polygon from anon-simple boundary line.

According to the OGC Specifications, a simple geometry is one that has no anomalous geometric points, such as self intersectionor self tangency and primarily refers to 0 or 1-dimensional geometries (i.e. [MULTI]POINT, [MULTI]LINESTRING).Geometry validity, on the other hand, primarily refers to 2-dimensional geometries (i.e. [MULTI]POLYGON) and defines theset of assertions that characterizes a valid polygon. The description of each geometric class includes specific conditions thatfurther detail geometric simplicity and validity.

A POINT is inheritably simple as a 0-dimensional geometry object.

MULTIPOINTs are simple if no two coordinates (POINTs) are equal (have identical coordinate values).

A LINESTRING is simple if it does not pass through the same POINT twice (except for the endpoints, in which case it is referredto as a linear ring and additionally considered closed).

(a) (b)


(c) (d)

(a) and (c) are simple LINESTRINGs, (b) and (d) are not.

A MULTILINESTRING is simple only if all of its elements are simple and the only intersection between any two elementsoccurs at POINTs that are on the boundaries of both elements.

(e) (f) (g)

(e) and (f) are simple MULTILINESTRINGs, (g) is not.

By definition, a POLYGON is always simple. It is valid if no two rings in the boundary (made up of an exterior ring and interiorrings) cross. The boundary of a POLYGON may intersect at a POINT but only as a tangent (i.e. not on a line). A POLYGON maynot have cut lines or spikes and the interior rings must be contained entirely within the exterior ring.


(h) (i) (j)

(k) (l) (m)

(h) and (i) are valid POLYGONs, (j-m) cannot be represented as single POLYGONs, but (j) and (m) could be represented asa valid MULTIPOLYGON.

A MULTIPOLYGON is valid if and only if all of its elements are valid and the interiors of no two elements intersect. Theboundaries of any two elements may touch, but only at a finite number of POINTs.


(n) (o)

(n) and (o) are not valid MULTIPOLYGONs. (p), however, is valid.

Most of the functions implemented by the GEOS library rely on the assumption that your geometries are valid as specified bythe OpenGIS Simple Feature Specification. To check simplicity or validity of geometries you can use the ST_IsSimple() andST_IsValid()

-- Typically, it doesn’t make sense to check-- for validity on linear features since it will always return TRUE.-- But in this example, PostGIS extends the definition of the OGC IsValid-- by returning false if a LineString has less than 2 *distinct* vertices.gisdb=# SELECT

ST_IsValid(’LINESTRING(0 0, 1 1)’),ST_IsValid(’LINESTRING(0 0, 0 0, 0 0)’);

st_isvalid | st_isvalid------------+-----------

t | f

By default, PostGIS does not apply this validity check on geometry input, because testing for validity needs lots of CPU time forcomplex geometries, especially polygons. If you do not trust your data sources, you can manually enforce such a check to yourtables by adding a check constraint:

ALTER TABLE mytableADD CONSTRAINT geometry_valid_checkCHECK (ST_IsValid(the_geom));

If you encounter any strange error messages such as "GEOS Intersection() threw an error!" or "JTS Intersection() threw an error!"when calling PostGIS functions with valid input geometries, you likely found an error in either PostGIS or one of the librariesit uses, and you should contact the PostGIS developers. The same is true if a PostGIS function returns an invalid geometry forvalid input.

NoteStrictly compliant OGC geometries cannot have Z or M values. The ST_IsValid() function won’t consider higher dimen-sioned geometries invalid! Invocations of AddGeometryColumn() will add a constraint checking geometry dimensions,so it is enough to specify 2 there.


4.3.6 Dimensionally Extended 9 Intersection Model (DE-9IM)

It is sometimes the case that the typical spatial predicates (ST_Contains, ST_Crosses, ST_Intersects, ST_Touches, ...) areinsufficient in and of themselves to adequately provide that desired spatial filter.

For example, consider a linear dataset representing a road network. It may be the task of a GIS analyst to identify all roadsegments that cross each other, not at a point, but on a line, perhaps invalidating some business rule. In this case,ST_Crosses does not adequately provide the necessary spatial filter since, for linear features, it returns true only wherethey cross at a point.One two-step solution might be to first perform the actual intersection (ST_Intersection) of pairs of road segments thatspatially intersect (ST_Intersects), and then compare the intersection’s ST_GeometryType with ’LINESTRING’ (properlydealing with cases that return GEOMETRYCOLLECTIONs of [MULTI]POINTs, [MULTI]LINESTRINGs, etc.).A more elegant / faster solution may indeed be desirable.


A second [theoretical] example may be that of a GIS analyst trying to locate all wharfs or docks that intersect a lake’sboundary on a line and where only one end of the wharf is up on shore. In other words, where a wharf is within, but notcompletely within a lake, intersecting the boundary of a lake on a line, and where the wharf’s endpoints are bothcompletely within and on the boundary of the lake. The analyst may need to use a combination of spatial predicates toisolate the sought after features:

• ST_Contains(lake, wharf) = TRUE

• ST_ContainsProperly(lake, wharf) = FALSE

• ST_GeometryType(ST_Intersection(wharf, lake)) = ’LINESTRING’

• ST_NumGeometries(ST_Multi(ST_Intersection(ST_Boundary(wharf), ST_Boundary(lake)))) = 1

... (needless to say, this could get quite complicated)

So enters the Dimensionally Extended 9 Intersection Model, or DE-9IM for short.

4.3.6.1 Theory

According to the OpenGIS Simple Features Implementation Specification for SQL, "the basic approach to comparing two ge-ometries is to make pair-wise tests of the intersections between the Interiors, Boundaries and Exteriors of the two geometries andto classify the relationship between the two geometries based on the entries in the resulting ’intersection’ matrix."

BoundaryThe boundary of a geometry is the set of geometries of the next lower dimension. For POINTs, which have a dimension of0, the boundary is the empty set. The boundary of a LINESTRING are the two endpoints. For POLYGONs, the boundaryis the linework that make up the exterior and interior rings.

InteriorThe interior of a geometry are those points of a geometry that are left when the boundary is removed. For POINTs,the interior is the POINT itself. The interior of a LINESTRING are the set of real points between the endpoints. ForPOLYGONs, the interior is the areal surface inside the polygon.

ExteriorThe exterior of a geometry is the universe, an areal surface, not on the interior or boundary of the geometry.



Given geometry a, where the I(a), B(a), and E(a) are the Interior, Boundary, and Exterior of a, the mathematical representationof the matrix is:

Interior Boundary ExteriorInterior dim( I(a) ∩ I(b) ) dim( I(a) ∩ B(b) ) dim( I(a) ∩ E(b) )

Boundary dim( B(a) ∩ I(b) ) dim( B(a) ∩ B(b) ) dim( B(a) ∩ E(b) )Exterior dim( E(a) ∩ I(b) ) dim( E(a) ∩ B(b) ) dim( E(a) ∩ E(b) )

Where dim(a) is the dimension of a as specified by ST_Dimension but has the domain of {0,1,2,T,F,*}

• 0 => point

• 1 => line

• 2 => area

• T => {0,1,2}

• F => empty set

• * => don’t care

Visually, for two overlapping polygonal geometries, this looks like:


Interior Boundary Exterior

Interior

dim(...) = 2 dim(...) = 1 dim(...) = 2

Boundary

dim(...) = 1 dim(...) = 0 dim(...) = 1

Exterior

dim(...) = 2 dim(...) = 1 dim(...) = 2

Read from left to right and from top to bottom, the dimensional matrix is represented, ’212101212’.

A relate matrix that would therefore represent our first example of two lines that intersect on a line would be: ’1*1***1**’

-- Identify road segments that cross on a lineSELECT a.idFROM roads a, roads bWHERE a.id != b.idAND a.geom && b.geomAND ST_Relate(a.geom, b.geom, ’1*1***1**’);

A relate matrix that represents the second example of wharfs partly on the lake’s shoreline would be ’102101FF2’

-- Identify wharfs partly on a lake’s shorelineSELECT a.lake_id, b.wharf_idFROM lakes a, wharfs bWHERE a.geom && b.geomAND ST_Relate(a.geom, b.geom, ’102101FF2’);


For more information or reading, see:

• OpenGIS Simple Features Implementation Specification for SQL (version 1.1, section 2.1.13.2)

• Dimensionally Extended Nine-Intersection Model (DE-9IM) by Christian Strobl

• GeoTools: Point Set Theory and the DE-9IM Matrix

• Encyclopedia of GIS By Hui Xiong

4.4 Loading GIS Data

Once you have created a spatial table, you are ready to upload GIS data to the database. Currently, there are two ways to get datainto a PostGIS/PostgreSQL database: using formatted SQL statements or using the Shape file loader/dumper.

4.4.1 Using SQL

If you can convert your data to a text representation, then using formatted SQL might be the easiest way to get your data intoPostGIS. As with Oracle and other SQL databases, data can be bulk loaded by piping a large text file full of SQL "INSERT"statements into the SQL terminal monitor.

A data upload file (roads.sql for example) might look like this:

BEGIN;INSERT INTO roads (road_id, roads_geom, road_name)

VALUES (1,ST_GeomFromText(’LINESTRING(191232 243118,191108 243242)’,-1),’Jeff Rd’);INSERT INTO roads (road_id, roads_geom, road_name)

VALUES (2,ST_GeomFromText(’LINESTRING(189141 244158,189265 244817)’,-1),’Geordie Rd’);INSERT INTO roads (road_id, roads_geom, road_name)

VALUES (3,ST_GeomFromText(’LINESTRING(192783 228138,192612 229814)’,-1),’Paul St’);INSERT INTO roads (road_id, roads_geom, road_name)

VALUES (4,ST_GeomFromText(’LINESTRING(189412 252431,189631 259122)’,-1),’Graeme Ave’);INSERT INTO roads (road_id, roads_geom, road_name)

VALUES (5,ST_GeomFromText(’LINESTRING(190131 224148,190871 228134)’,-1),’Phil Tce’);INSERT INTO roads (road_id, roads_geom, road_name)

VALUES (6,ST_GeomFromText(’LINESTRING(198231 263418,198213 268322)’,-1),’Dave Cres’);COMMIT;

The data file can be piped into PostgreSQL very easily using the "psql" SQL terminal monitor:

psql -d [database] -f roads.sql

4.4.2 Using the Loader

The shp2pgsql data loader converts ESRI Shape files into SQL suitable for insertion into a PostGIS/PostgreSQL databaseeither in geometry or geography format. The loader has several operating modes distinguished by command line flags:

In addition to the shp2pgsql command-line loader, there is an shp2pgsql-gui graphical interface with most of the options asthe command-line loader, but may be easier to use for one-off non-scripted loading or if you are new to PostGIS. It can also beconfigured as a plugin to PgAdminIII.

(c|a|d|p) These are mutually exclusive options:

-c Creates a new table and populates it from the shapefile. This is the default mode.

-a Appends data from the Shape file into the database table. Note that to use this option to load multiple files, the filesmust have the same attributes and same data types.

-d Drops the database table before creating a new table with the data in the Shape file.


http://gis.hsr.ch/wiki/images/3/3d/9dem_springer.pdf

http://docs.geotools.org/latest/userguide/library/jts/dim9.html


-p Only produces the table creation SQL code, without adding any actual data. This can be used if you need to completelyseparate the table creation and data loading steps.

-? Display help screen.

-D Use the PostgreSQL "dump" format for the output data. This can be combined with -a, -c and -d. It is much faster to loadthan the default "insert" SQL format. Use this for very large data sets.

-s [<FROM_SRID%gt;:]<SRID> Creates and populates the geometry tables with the specified SRID. Optionally specifies thatthe input shapefile uses the given FROM_SRID, in which case the geometries will be reprojected to the target SRID.FROM_SRID cannot be specified with -D.

-k Keep identifiers’ case (column, schema and attributes). Note that attributes in Shapefile are all UPPERCASE.

-i Coerce all integers to standard 32-bit integers, do not create 64-bit bigints, even if the DBF header signature appears to warrantit.

-I Create a GiST index on the geometry column.

-S Generate simple geometries instead of MULTI geometries. Will only succeed if all the geometries are actually single (I.E. aMULTIPOLYGON with a single shell, or or a MULTIPOINT with a single vertex).

-t <dimensionality> Force the output geometry to have the specified dimensionality. Use the following strings to indicate thedimensionality: 2D, 3DZ, 3DM, 4D.

If the input has fewer dimensions that specified, the output will have those dimensions filled in with zeroes. If the inputhas more dimensions that specified, the unwanted dimensions will be stripped.

-w Output WKT format, instead of WKB. Note that this can introduce coordinate drifts due to loss of precision.

-e Execute each statement on its own, without using a transaction. This allows loading of the majority of good data when thereare some bad geometries that generate errors. Note that this cannot be used with the -D flag as the "dump" format alwaysuses a transaction.

-W <encoding> Specify encoding of the input data (dbf file). When used, all attributes of the dbf are converted from thespecified encoding to UTF8. The resulting SQL output will contain a SET CLIENT_ENCODING to UTF8 command,so that the backend will be able to reconvert from UTF8 to whatever encoding the database is configured to use internally.

-N <policy> NULL geometries handling policy (insert*,skip,abort)

-n -n Only import DBF file. If your data has no corresponding shapefile, it will automatically switch to this mode and load justthe dbf. So setting this flag is only needed if you have a full shapefile set, and you only want the attribute data and nogeometry.

-G Use geography type instead of geometry (requires lon/lat data) in WGS84 long lat (SRID=4326)

-T <tablespace> Specify the tablespace for the new table. Indexes will still use the default tablespace unless the -X parameteris also used. The PostgreSQL documentation has a good description on when to use custom tablespaces.

-X <tablespace> Specify the tablespace for the new table’s indexes. This applies to the primary key index, and the GIST spatialindex if -I is also used.

An example session using the loader to create an input file and uploading it might look like this:

# shp2pgsql -c -D -s 4269 -i -I shaperoads.shp myschema.roadstable > roads.sql# psql -d roadsdb -f roads.sql

A conversion and upload can be done all in one step using UNIX pipes:

# shp2pgsql shaperoads.shp myschema.roadstable | psql -d roadsdb


4.5 Retrieving GIS Data

Data can be extracted from the database using either SQL or the Shape file loader/dumper. In the section on SQL we will discusssome of the operators available to do comparisons and queries on spatial tables.

4.5.1 Using SQL

The most straightforward means of pulling data out of the database is to use a SQL select query to reduce the number ofRECORDS and COLUMNS returned and dump the resulting columns into a parsable text file:

db=# SELECT road_id, ST_AsText(road_geom) AS geom, road_name FROM roads;

road_id | geom | road_name--------+-----------------------------------------+-----------

1 | LINESTRING(191232 243118,191108 243242) | Jeff Rd2 | LINESTRING(189141 244158,189265 244817) | Geordie Rd3 | LINESTRING(192783 228138,192612 229814) | Paul St4 | LINESTRING(189412 252431,189631 259122) | Graeme Ave5 | LINESTRING(190131 224148,190871 228134) | Phil Tce6 | LINESTRING(198231 263418,198213 268322) | Dave Cres7 | LINESTRING(218421 284121,224123 241231) | Chris Way

(6 rows)

However, there will be times when some kind of restriction is necessary to cut down the number of fields returned. In the case ofattribute-based restrictions, just use the same SQL syntax as normal with a non-spatial table. In the case of spatial restrictions,the following operators are available/useful:

&& This operator tells whether the bounding box of one geometry intersects the bounding box of another.

ST_OrderingEquals This tests whether two geometries are geometrically identical. For example, if ’POLYGON((0 0,1 1,1 0,00))’ is the same as ’POLYGON((0 0,1 1,1 0,0 0))’ (it is).

= This operator is a little more naive, it only tests whether the bounding boxes of two geometries are the same.

Next, you can use these operators in queries. Note that when specifying geometries and boxes on the SQL command line,you must explicitly turn the string representations into geometries by using the "ST_GeomFromText()" function. The 312 is afictitious spatial reference system that matches our data. So, for example:

SELECT road_id, road_nameFROM roadsWHERE ST_OrderingEquals(roads_geom , ST_GeomFromText(’LINESTRING(191232 243118,191108 ←↩

243242)’,312) ) ;

The above query would return the single record from the "ROADS_GEOM" table in which the geometry was equal to that value.

When using the "&&" operator, you can specify either a BOX3D as the comparison feature or a GEOMETRY. When you specifya GEOMETRY, however, its bounding box will be used for the comparison.

SELECT road_id, road_nameFROM roadsWHERE roads_geom && ST_GeomFromText(’POLYGON((...))’,312);

The above query will use the bounding box of the polygon for comparison purposes.

The most common spatial query will probably be a "frame-based" query, used by client software, like data browsers and webmappers, to grab a "map frame" worth of data for display. Using a "BOX3D" object for the frame, such a query looks like this:

SELECT ST_AsText(roads_geom) AS geomFROM roadsWHERE

roads_geom && ST_MakeEnvelope(191232, 243117,191232, 243119,312);

Note the use of the SRID 312, to specify the projection of the envelope.


4.5.2 Using the Dumper

The pgsql2shp table dumper connects directly to the database and converts a table (possibly defined by a query) into a shapefile. The basic syntax is:

pgsql2shp [<options>] <database> [<schema>.]<table>

pgsql2shp [<options>] <database> <query>

The commandline options are:

-f <filename> Write the output to a particular filename.

-h <host> The database host to connect to.

-p <port> The port to connect to on the database host.

-P <password> The password to use when connecting to the database.

-u <user> The username to use when connecting to the database.

-g <geometry column> In the case of tables with multiple geometry columns, the geometry column to use when writing theshape file.

-b Use a binary cursor. This will make the operation faster, but will not work if any NON-geometry attribute in the table lacks acast to text.

-r Raw mode. Do not drop the gid field, or escape column names.

-d For backward compatibility: write a 3-dimensional shape file when dumping from old (pre-1.0.0) postgis databases (thedefault is to write a 2-dimensional shape file in that case). Starting from postgis-1.0.0+, dimensions are fully encoded.

-m filename Remap identifiers to ten character names. The content of the file is lines of two symbols separated by a singlewhite space and no trailing or leading space: VERYLONGSYMBOL SHORTONE ANOTHERVERYLONGSYMBOLSHORTER etc.

4.6 Building Indexes

Indexes are what make using a spatial database for large data sets possible. Without indexing, any search for a feature wouldrequire a "sequential scan" of every record in the database. Indexing speeds up searching by organizing the data into a searchtree which can be quickly traversed to find a particular record. PostgreSQL supports three kinds of indexes by default: B-Treeindexes, R-Tree indexes, and GiST indexes.

• B-Trees are used for data which can be sorted along one axis; for example, numbers, letters, dates. GIS data cannot be rationallysorted along one axis (which is greater, (0,0) or (0,1) or (1,0)?) so B-Tree indexing is of no use for us.

• R-Trees break up data into rectangles, and sub-rectangles, and sub-sub rectangles, etc. R-Trees are used by some spatialdatabases to index GIS data, but the PostgreSQL R-Tree implementation is not as robust as the GiST implementation.

• GiST (Generalized Search Trees) indexes break up data into "things to one side", "things which overlap", "things which areinside" and can be used on a wide range of data-types, including GIS data. PostGIS uses an R-Tree index implemented on topof GiST to index GIS data.


4.6.1 GiST Indexes

GiST stands for "Generalized Search Tree" and is a generic form of indexing. In addition to GIS indexing, GiST is used to speedup searches on all kinds of irregular data structures (integer arrays, spectral data, etc) which are not amenable to normal B-Treeindexing.

Once a GIS data table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data(unless all your searches are based on attributes, in which case you’ll want to build a normal index on the attribute fields).

The syntax for building a GiST index on a "geometry" column is as follows:

CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometryfield] );

The above syntax will always build a 2D-index. To get the an n-dimensional index supported in PostGIS 2.0+ for the geometrytype, you can create one using this syntax

CREATE INDEX [indexname] ON [tablename] USING GIST ([geometryfield] gist_geometry_ops_nd);

Building a spatial index is a computationally intensive exercise: on tables of around 1 million rows, on a 300MHz Solarismachine, we have found building a GiST index takes about 1 hour. After building an index, it is important to force PostgreSQLto collect table statistics, which are used to optimize query plans:

VACUUM ANALYZE [table_name] [(column_name)];-- This is only needed for PostgreSQL 7.4 installations and belowSELECT UPDATE_GEOMETRY_STATS([table_name], [column_name]);

GiST indexes have two advantages over R-Tree indexes in PostgreSQL. Firstly, GiST indexes are "null safe", meaning they canindex columns which include null values. Secondly, GiST indexes support the concept of "lossiness" which is important whendealing with GIS objects larger than the PostgreSQL 8K page size. Lossiness allows PostgreSQL to store only the "important"part of an object in an index -- in the case of GIS objects, just the bounding box. GIS objects larger than 8K will cause R-Treeindexes to fail in the process of being built.

4.6.2 Using Indexes

Ordinarily, indexes invisibly speed up data access: once the index is built, the query planner transparently decides when to useindex information to speed up a query plan. Unfortunately, the PostgreSQL query planner does not optimize the use of GiSTindexes well, so sometimes searches which should use a spatial index instead default to a sequence scan of the whole table.

If you find your spatial indexes are not being used (or your attribute indexes, for that matter) there are a couple things you cando:

• Firstly, make sure statistics are gathered about the number and distributions of values in a table, to provide the query plan-ner with better information to make decisions around index usage. For PostgreSQL 7.4 installations and below this is doneby running update_geometry_stats([table_name, column_name]) (compute distribution) and VACUUM ANALYZE [ta-ble_name] [column_name] (compute number of values). Starting with PostgreSQL 8.0 running VACUUM ANALYZE willdo both operations. You should regularly vacuum your databases anyways -- many PostgreSQL DBAs have VACUUM run asan off-peak cron job on a regular basis.

• If vacuuming does not work, you can force the planner to use the index information by using the SET ENABLE_SEQSCAN=OFFcommand. You should only use this command sparingly, and only on spatially indexed queries: generally speaking, the plannerknows better than you do about when to use normal B-Tree indexes. Once you have run your query, you should consider settingENABLE_SEQSCAN back on, so that other queries will utilize the planner as normal.

NoteAs of version 0.6, it should not be necessary to force the planner to use the index with ENABLE_SEQSCAN.

• If you find the planner wrong about the cost of sequential vs index scans try reducing the value of random_page_cost inpostgresql.conf or using SET random_page_cost=#. Default value for the parameter is 4, try setting it to 1 or 2. Decrementingthe value makes the planner more inclined of using Index scans.


4.7 Complex Queries

The raison d’etre of spatial database functionality is performing queries inside the database which would ordinarily requiredesktop GIS functionality. Using PostGIS effectively requires knowing what spatial functions are available, and ensuring thatappropriate indexes are in place to provide good performance. The SRID of 312 used in these examples is purely for demonstra-tion. You should be using a REAL SRID listed in the the spatial_ref_sys table and one that matches the projection of your data.If your data has no spatial reference system specified, you should be THINKING very thoughtfully why it doesn’t and maybe itshould. If your reason is because you are modeling something that doesn’t have a geographic spatial reference system definedsuch as the internals of a molecule or a good location on Mars to transport the human race in the event of a nuclear holocaust,then simply leave out the SRID or make one up and insert it in the spatial_ref_sys table.

4.7.1 Taking Advantage of Indexes

When constructing a query it is important to remember that only the bounding-box-based operators such as && can take ad-vantage of the GiST spatial index. Functions such as ST_Distance() cannot use the index to optimize their operation. Forexample, the following query would be quite slow on a large table:

SELECT the_geomFROM geom_tableWHERE ST_Distance(the_geom, ST_GeomFromText(’POINT(100000 200000)’, 312)) < 100

This query is selecting all the geometries in geom_table which are within 100 units of the point (100000, 200000). It will beslow because it is calculating the distance between each point in the table and our specified point, ie. one ST_Distance()calculation for each row in the table. We can avoid this by using the && operator to reduce the number of distance calculationsrequired:

SELECT the_geomFROM geom_tableWHERE ST_DWithin(the_geom, ST_MakeEnvelope(90900, 190900, 100100, 200100,312), 100)

This query selects the same geometries, but it does it in a more efficient way. Assuming there is a GiST index on the_geom, thequery planner will recognize that it can use the index to reduce the number of rows before calculating the result of the ST_dis-tance() function. Notice that the ST_MakeEnvelope geometry which is used in the && operation is a 200 unit square boxcentered on the original point - this is our "query box". The && operator uses the index to quickly reduce the result set down toonly those geometries which have bounding boxes that overlap the "query box". Assuming that our query box is much smallerthan the extents of the entire geometry table, this will drastically reduce the number of distance calculations that need to be done.

Change in BehaviorAs of PostGIS 1.3.0, most of the Geometry Relationship Functions, with the notable exceptions of ST_Disjoint andST_Relate, include implicit bounding box overlap operators.

4.7.2 Examples of Spatial SQL

The examples in this section will make use of two tables, a table of linear roads, and a table of polygonal municipality boundaries.The table definitions for the bc_roads table is:

Column | Type | Description------------+-------------------+-------------------gid | integer | Unique IDname | character varying | Road Namethe_geom | geometry | Location Geometry (Linestring)

The table definition for the bc_municipality table is:


Column | Type | Description-----------+-------------------+-------------------gid | integer | Unique IDcode | integer | Unique IDname | character varying | City / Town Namethe_geom | geometry | Location Geometry (Polygon)

1. What is the total length of all roads, expressed in kilometers?

You can answer this question with a very simple piece of SQL:

SELECT sum(ST_Length(the_geom))/1000 AS km_roads FROM bc_roads;

km_roads------------------70842.1243039643(1 row)

2. How large is the city of Prince George, in hectares?

This query combines an attribute condition (on the municipality name) with a spatial calculation (of the area):

SELECTST_Area(the_geom)/10000 AS hectares

FROM bc_municipalityWHERE name = ’PRINCE GEORGE’;

hectares------------------32657.9103824927(1 row)

3. What is the largest municipality in the province, by area?

This query brings a spatial measurement into the query condition. There are several ways of approaching this problem, butthe most efficient is below:

SELECTname,ST_Area(the_geom)/10000 AS hectares

FROMbc_municipality

ORDER BY hectares DESCLIMIT 1;

name | hectares---------------+-----------------TUMBLER RIDGE | 155020.02556131(1 row)

Note that in order to answer this query we have to calculate the area of every polygon. If we were doing this a lot it wouldmake sense to add an area column to the table that we could separately index for performance. By ordering the results in adescending direction, and them using the PostgreSQL "LIMIT" command we can easily pick off the largest value withoutusing an aggregate function like max().

4. What is the length of roads fully contained within each municipality?

This is an example of a "spatial join", because we are bringing together data from two tables (doing a join) but using aspatial interaction condition ("contained") as the join condition rather than the usual relational approach of joining on acommon key:


SELECTm.name,sum(ST_Length(r.the_geom))/1000 as roads_km

FROMbc_roads AS r,bc_municipality AS m

WHEREST_Contains(m.the_geom,r.the_geom)

GROUP BY m.nameORDER BY roads_km;

name | roads_km----------------------------+------------------SURREY | 1539.47553551242VANCOUVER | 1450.33093486576LANGLEY DISTRICT | 833.793392535662BURNABY | 773.769091404338PRINCE GEORGE | 694.37554369147...

This query takes a while, because every road in the table is summarized into the final result (about 250K roads for ourparticular example table). For smaller overlays (several thousand records on several hundred) the response can be veryfast.

5. Create a new table with all the roads within the city of Prince George.

This is an example of an "overlay", which takes in two tables and outputs a new table that consists of spatially clipped orcut resultants. Unlike the "spatial join" demonstrated above, this query actually creates new geometries. An overlay is likea turbo-charged spatial join, and is useful for more exact analysis work:

CREATE TABLE pg_roads asSELECTST_Intersection(r.the_geom, m.the_geom) AS intersection_geom,ST_Length(r.the_geom) AS rd_orig_length,r.*

FROMbc_roads AS r,bc_municipality AS m

WHERE m.name = ’PRINCE GEORGE’ AND ST_Intersects(r.the_geom, m.the_geom);

6. What is the length in kilometers of "Douglas St" in Victoria?

SELECTsum(ST_Length(r.the_geom))/1000 AS kilometers

FROMbc_roads r,bc_municipality m

WHERE r.name = ’Douglas St’ AND m.name = ’VICTORIA’AND ST_Contains(m.the_geom, r.the_geom) ;

kilometers------------------4.89151904172838(1 row)

7. What is the largest municipality polygon that has a hole?

SELECT gid, name, ST_Area(the_geom) AS areaFROM bc_municipalityWHERE ST_NRings(the_geom) > 1ORDER BY area DESC LIMIT 1;


gid | name | area-----+--------------+------------------12 | SPALLUMCHEEN | 257374619.430216(1 row)


Chapter 5

Raster Data Management, Queries, and Applica-tions

5.1 Loading and Creating Rasters

For most use cases, you will create PostGIS rasters by loading existing raster files using the packaged raster2pgsql rasterloader.

5.1.1 Using raster2pgsql to load rasters

The raster2pgsql is a raster loader executable that loads GDAL supported raster formats into sql suitable for loading into aPostGIS raster table. It is capable of loading folders of raster files as well as creating overviews of rasters.

Since the raster2pgsql is compiled as part of PostGIS most often (unless you compile your own GDAL library), the raster typessupported by the executable will be the same as those compiled in the GDAL dependency library. To get a list of raster typesyour particular raster2pgsql supports use the -G switch. These should be the same as those provided by your PostGIS installdocumented here ST_GDALDrivers if you are using the same gdal library for both.

NoteThe older version of this tool was a python script. The executable has replaced the python script. If you still find theneed for the Python script Examples of the python one can be found at GDAL PostGIS Raster Driver Usage. Pleasenote that the raster2pgsql python script may not work with future versions of PostGIS raster and is no longer supported.

NoteWhen creating overviews of a specific factor from a set of rasters that are aligned, it is possible for the overviews to notalign. Visit http://trac.osgeo.org/postgis/ticket/1764 for an example where the overviews do not align.

EXAMPLE USAGE:

raster2pgsql raster_options_go_here raster_file someschema.sometable > out.sql

-? Display help screen. Help will also display if you don’t pass in any arguments.

-G Print the supported raster formats.

(c|a|d|p) These are mutually exclusive options:

http://trac.osgeo.org/gdal/wiki/frmts_wtkraster.html



-c Create new table and populate it with raster(s), this is the default mode

-a Append raster(s) to an existing table.

-d Drop table, create new one and populate it with raster(s)

-p Prepare mode, only create the table.

Raster processing: Applying constraints for proper registering in raster catalogs

-C Apply raster constraints -- srid, pixelsize etc. to ensure raster is properly registered in raster_columns view.

-x Disable setting the max extent constraint. Only applied if -C flag is also used.

-r Set the regular blocking constraint. Only applied if -C flag is also used.

Raster processing: Optional parameters used to manipulate input raster dataset

-s <SRID> Assign output raster with specified SRID.

-b BAND Index (1-based) of band to extract from raster. For more than one band index, separate with comma (,). Ifunspecified, all bands of raster will be extracted.

-t TILE_SIZE Cut raster into tiles to be inserted one per table row. TILE_SIZE is expressed as WIDTHxHEIGHT.

-R, --register Register the raster as a filesystem (out-db) raster.Only the metadata of the raster and path location to the raster is stored in the database (not the pixels).

-l OVERVIEW_FACTOR Create overview of the raster. For more than one factor, separate with comma(,). Overviewtable name follows the pattern o_overview factor_table, where overview factor is a placeholder fornumerical overview factor and table is replaced with the base table name. Created overview is stored in thedatabase and is not affected by -R. Note that your generated sql file will contain both the main table and overviewtables.

-N NODATA NODATA value to use on bands without a NODATA value.

Optional parameters used to manipulate database objects

-q Wrap PostgreSQL identifiers in quotes

-f COLUMN Specify name of destination raster column, default is ’rast’

-F Add a column with the name of the file

-I Create a GiST index on the raster column.

-M Vacuum analyze the raster table.

-T tablespace Specify the tablespace for the new table. Note that indices (including the primary key) will still use thedefault tablespace unless the -X flag is also used.

-X tablespace Specify the tablespace for the table’s new index. This applies to the primary key and the spatial indexif the -I flag is used.

-Y Use copy statements instead of insert statements.

-e Execute each statement individually, do not use a transaction.

-E ENDIAN Control endianness of generated binary output of raster; specify 0 for XDR and 1 for NDR (default); only NDRoutput is supported now

-V version Specify version of output format. Default is 0. Only 0 is supported at this time.

An example session using the loader to create an input file and uploading it chunked in 100x100 tiles might look like this:

NoteYou can leave the schema name out e.g demelevation instead of public.demelevation and the raster tablewill be created in the default schema of the database or user


raster2pgsql -s 4236 -I -C -M *.tif -F -t 100x100 public.demelevation > elev.sqlpsql -d gisdb -f elev.sql

A conversion and upload can be done all in one step using UNIX pipes:

raster2pgsql -s 4236 -I -C -M *.tif -F -t 100x100 public.demelevation | psql -d gisdb

Load rasters Massachusetts state plane meters aerial tiles into a schema called aerial and create a full view, 2 and 4 leveloverview tables, use copy mode for inserting (no intermediary file just straight to db), and -e don’t force everything in a transaction(good if you want to see data in tables right away without waiting). Break up the rasters into 128x128 pixel tiles and apply rasterconstraints. Use copy mode instead of table insert. (-F) Include a field called filename to hold the name of the file the tiles werecut from.

raster2pgsql -I -C -e -Y -F -s 26986 -t 128x128 -l 2,4 bostonaerials2008/*.jpg aerials. ←↩boston | psql -U postgres -d gisdb -h localhost -p 5432

--get a list of raster types supported:raster2pgsql -G

The -G commands outputs a list something like

Available GDAL raster formats:Virtual RasterGeoTIFFNational Imagery Transmission FormatRaster Product Format TOC formatECRG TOC formatErdas Imagine Images (.img)CEOS SAR ImageCEOS ImageJAXA PALSAR Product Reader (Level 1.1/1.5)Ground-based SAR Applications Testbed File Format (.gff)ELASArc/Info Binary GridArc/Info ASCII GridGRASS ASCII GridSDTS RasterDTED Elevation RasterPortable Network GraphicsJPEG JFIFIn Memory RasterJapanese DEM (.mem)Graphics Interchange Format (.gif)Graphics Interchange Format (.gif)Envisat Image FormatMaptech BSB Nautical ChartsX11 PixMap FormatMS Windows Device Independent BitmapSPOT DIMAPAirSAR Polarimetric ImageRadarSat 2 XML ProductPCIDSK Database FilePCRaster Raster FileILWIS Raster MapSGI Image File Format 1.0SRTMHGT File FormatLeveller heightfieldTerragen heightfieldUSGS Astrogeology ISIS cube (Version 3)USGS Astrogeology ISIS cube (Version 2)


NASA Planetary Data SystemEarthWatch .TILERMapper .ers LabelledNOAA Polar Orbiter Level 1b Data SetFIT ImageGRIdded Binary (.grb)Raster Matrix FormatEUMETSAT Archive native (.nat)Idrisi Raster A.1Intergraph RasterGolden Software ASCII Grid (.grd)Golden Software Binary Grid (.grd)Golden Software 7 Binary Grid (.grd)COSAR Annotated Binary Matrix (TerraSAR-X)TerraSAR-X ProductDRDC COASP SAR Processor RasterR Object Data StorePortable Pixmap Format (netpbm)USGS DOQ (Old Style)USGS DOQ (New Style)ENVI .hdr LabelledESRI .hdr LabelledGeneric Binary (.hdr Labelled)PCI .aux LabelledVexcel MFF RasterVexcel MFF2 (HKV) RasterFuji BAS Scanner ImageGSC GeogridEOSAT FAST FormatVTP .bt (Binary Terrain) 1.3 FormatErdas .LAN/.GISConvair PolGASPImage Data and AnalysisNLAPS Data FormatErdas Imagine RawDIPExFARSITE v.4 Landscape File (.lcp)NOAA Vertical Datum .GTXNADCON .los/.las Datum Grid ShiftNTv2 Datum Grid ShiftACE2Snow Data Assimilation SystemSwedish Grid RIK (.rik)USGS Optional ASCII DEM (and CDED)GeoSoft Grid Exchange FormatNorthwood Numeric Grid Format .grd/.tabNorthwood Classified Grid Format .grc/.tabARC Digitized Raster GraphicsStandard Raster Product (ASRP/USRP)Magellan topo (.blx)SAGA GIS Binary Grid (.sdat)Kml Super OverlayASCII Gridded XYZHF2/HFZ heightfield rasterOziExplorer Image FileUSGS LULC Composite Theme GridArc/Info Export E00 GRIDZMap Plus GridNOAA NGS Geoid Height Grids


5.1.2 Creating rasters using PostGIS raster functions

On many occasions, you’ll want to create rasters and raster tables right in the database. There are a plethora of functions to dothat. The general steps to follow.

1. Create a table with a raster column to hold the new raster records which can be accomplished with:

CREATE TABLE myrasters(rid serial primary key, rast raster);

2. There are many functions to help with that goal. If you are creating rasters not as a derivative of other rasters, you willwant to start with: ST_MakeEmptyRaster, followed by ST_AddBand

You can also create rasters from geometries. To achieve that you’ll want to use ST_AsRaster perhaps accompanied withother functions such as ST_Union or ST_MapAlgebraFct or any of the family of other map algebra functions.

There are even many more options for creating new raster tables from existing tables. For example you can create a rastertable in a different projection from an existing one using ST_Transform

3. Once you are done populating your table initially, you’ll want to create a spatial index on the raster column with somethinglike:

CREATE INDEX myrasters_rast_st_convexhull_idx ON myrasters USING gist( ST_ConvexHull( ←↩rast) );

Note the use of ST_ConvexHull since most raster operators are based on the convex hull of the rasters.

NotePre-2.0 versions of PostGIS raster were based on the envelop rather than the convex hull. For teh spatial idnexesto work properly you’ll need to drop those and replace with convex hull based index.

4. Apply raster constraints using AddRasterConstraints

5.2 Raster Catalogs

There are two raster catalog views that come packaged with PostGIS. Both views utilize information embedded in the constraintsof the raster tables. As a result the catalog views are always consistent with the raster data in the tables since the constraints areenforced.

1. raster_columns this view catalogs all the raster table columns in your database.

2. raster_overviews this view catalogs all the raster table columns in your database that serve as overviews for a finergrained table. Tables of this type are generated when you use the -l switch during load.

5.2.1 Raster Columns Catalog

The raster_columns is a catalog of all raster table columns in your database that are of type raster. It is a view utilizing theconstraints on the tables so the information is always consistent even if you restore one raster table from a backup of anotherdatabase. The following columns exist in the raster_columns catalog.

If you created your tables not with the loader or forgot to specify the -C flag during load, you can enforce the constraints afterthe fact using AddRasterConstraints so that the raster_columns catalog registers the common information about your rastertiles.

• r_table_catalog The database the table is in. This will always read the current database.

• r_table_schema The database schema the raster table belongs to.


• r_table_name raster table

• r_raster_column the column in the r_table_name table that is of type raster. There is nothing in PostGIS preventingyou from having multiple raster columns per table so its possible to have a raster table listed multiple times with a differentraster column for each.

• srid The spatial reference identifier of the raster. Should be an entry in the Section 4.3.1.

• scale_x The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster columnhave the same scale_x and this constraint is applied. Refer to ST_ScaleX for more details.

• scale_y The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster columnhave the same scale_y and the scale_y constraint is applied. Refer to ST_ScaleY for more details.

• blocksize_x The width (number of pixels across) of each raster tile . Refer to ST_Width for more details.

• blocksize_y The width (number of pixels down) of each raster tile . Refer to ST_Height for more details.

• same_alignment A boolean that is true if all the raster tiles have the same alignment . Refer to ST_SameAlignment formore details.

• regular_blocking This is a true/false constraint flag set on the table to denote that the tiles do not overlap, are of thesame alignment, pixel size, srid etc. It is not really validated but just taken as a given so should be used for informational. Inthe future we plan to properly constrain this so that this inforamtion is guaranteed to be right when it returns true

• num_bands The number of bands in each tile of your raster set. This is the same information as what is provided byST_NumBands

• pixel_types An array defining the pixel type for each band. You will have the same number of elements in this array asyou have number of bands. The pixel_types are one of the following defined in ST_BandPixelType.

• nodata_values An array of double precision numbers denoting the nodata_value for each band. You will have thesame number of elements in this array as you have number of bands. These numbers define the pixel value for each band thatshould be ignored for most operations. This is similar information provided by ST_BandNoDataValue.

• extent This is the extent of all the raster rows in your raster set. If you plan to load more data that will change the extent of theset, you’ll want to run the DropRasterConstraints function before load and then reapply constraints with AddRasterConstraintsafter load.

5.2.2 Raster Overviews

raster_overviews catalogs information about raster table columns used for overviews and additional information aboutthem that is useful to know when utilizing overviews. Overview tables are cataloged in both raster_columns and raster-_overviews because they are rasters in their own right but also serve an additional special purpose of being a lower resolutioncaricature of a higher resolution table. These are generated along-side the main raster table when you use the -l switch in rasterloading.

Overview tables contain the same constraints as other raster tables as well as additional informational only constraints specific tooverviews.

NoteThe information in raster_overviews does not duplicate the information in raster_columns. If you needthe information about an overview table present in raster_columns you can join the raster_overviews andraster_columns together to get the full set of information you need.

Two main reasons for overviews are:

1. Low resolution representation of the core tables commonly used for fast mapping zoom-out.


2. Computations are generally faster to do on them than their higher resolution parents because there are fewer records andeach pixel covers more territory. Though the computations are not as accurate as the high-res tables they support, they canbe sufficient in many rule-of-thumb computations.

The raster_overviews catalog contains the following columns of information.

• o_table_catalog The database the overview table is in. This will always read the current database.

• o_table_schema The database schema the overview raster table belongs to.

• o_table_name raster overview table name

• o_raster_column the raster column in the overview table.

• r_table_catalog The database the raster table that this overview services is in. This will always read the current database.

• r_table_schema The database schema the raster table that this overview services belongs to.

• r_table_name raster table that this overview services.

• r_raster_column the raster column that this overview column services.

• overview_factor - this is the pyramid level of the overview table. The higher the number the lower the resolution ofthe table. raster2pgsql if given a folder of images, will compute overview of each image file and load separately. Level 1is assumed and always the original file. Level 2 is will have each tile represent 4 of the original. So for example if youhave a folder of 5000x5000 pixel image files that you chose to chunk 125x125, for each image file your base table will have(5000*5000)/(125*125) records = 1600, your (l=2) o_2 table will have ceiling(1600/Power(2,2)) = 400 rows, your (l=3) o_3will have ceiling(1600/Power(2,3) ) = 200 rows. If your pixels aren’t divisible by the size of your tiles, you’ll get some scraptiles (tiles not completely filled). Note that each overview tile generated by raster2pgsql has the same number of pixels as itsparent, but is of a lower resolution where each pixel of it represents (Power(2,overview_factor) pixels of the original).

5.3 Building Custom Applications with PostGIS Raster

The fact that PostGIS raster provides you with SQL functions to render rasters in known image formats gives you a lot of optoinsfor rendering them. For example you can use OpenOffice / LibreOffice for rendering as demonstrated in Rendering PostGISRaster graphics with LibreOffice Base Reports. In addition you can use a wide variety of languages as demonstrated in thissection.

5.3.1 PHP Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we’ll demonstrate how to use the PHP PostgreSQL driver and the ST_AsGDALRaster family of functions tooutput band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect aparticular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms touser specified projection using ST_Transform, and then outputs the results as a png using ST_AsPNG.

You would call the below using

http://mywebserver/test_raster.php?srid=2249

to get the raster image in Massachusetts state plane feet.

<?php/** contents of test_raster.php **/$conn_str =’dbname=mydb host=localhost port=5432 user=myuser password=mypwd’;$dbconn = pg_connect($conn_str);header(’Content-Type: image/png’);

http://www.postgresonline.com/journal/archives/244-Rendering-PostGIS-Raster-graphics-with-LibreOffice-Base-Reports.html

http://www.postgresonline.com/journal/archives/244-Rendering-PostGIS-Raster-graphics-with-LibreOffice-Base-Reports.html


/**If a particular projection was requested use it otherwise use mass state plane meters ←↩**/

if (!empty( $_REQUEST[’srid’] ) && is_numeric( $_REQUEST[’srid’]) ){$input_srid = intval($_REQUEST[’srid’]);

}else { $input_srid = 26986; }/** The set bytea_output may be needed for PostgreSQL 9.0+, but not for 8.4 **/$sql = "set bytea_output=’escape’;SELECT ST_AsPNG(ST_Transform(

ST_AddBand(ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)]),$input_srid) ) As new_rast

FROM aerials.bostonWHEREST_Intersects(rast, ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, ←↩

42.218,4326),26986) )";$result = pg_query($sql);$row = pg_fetch_row($result);pg_free_result($result);if ($row === false) return;echo pg_unescape_bytea($row[0]);?>

5.3.2 ASP.NET C# Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we’ll demonstrate how to use Npgsql PostgreSQL .NET driver and the ST_AsGDALRaster family of functionsto output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

You will need the npgsql .NET PostgreSQL driver for this exercise which you can get the latest of from http://npgsql.projects.postgresql.org/-. Just download the latest and drop into your ASP.NET bin folder and you’ll be good to go.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect aparticular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms touser specified projection using ST_Transform, and then outputs the results as a png using ST_AsPNG.

This is same example as Section 5.3.1 except implemented in C#.

You would call the below using

http://mywebserver/TestRaster.ashx?srid=2249

to get the raster image in Massachusetts state plane feet.

-- web.config connection string section --<connectionStrings>

<add name="DSN"connectionString="server=localhost;database=mydb;Port=5432;User Id=myuser;password= ←↩

mypwd"/></connectionStrings>

// Code for TestRaster.ashx<%@ WebHandler Language="C#" Class="TestRaster" %>using System;using System.Data;using System.Web;using Npgsql;

public class TestRaster : IHttpHandler{

public void ProcessRequest(HttpContext context){

http://npgsql.projects.postgresql.org/

http://npgsql.projects.postgresql.org/


context.Response.ContentType = "image/png";context.Response.BinaryWrite(GetResults(context));

}

public bool IsReusable {get { return false; }

}

public byte[] GetResults(HttpContext context){byte[] result = null;NpgsqlCommand command;string sql = null;int input_srid = 26986;

try {using (NpgsqlConnection conn = new NpgsqlConnection(System.Configuration. ←↩

ConfigurationManager.ConnectionStrings["DSN"].ConnectionString)) {conn.Open();

if (context.Request["srid"] != null){

input_srid = Convert.ToInt32(context.Request["srid"]);}sql = @"SELECT ST_AsPNG(

ST_Transform(ST_AddBand(

ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)]),:input_srid) ) As new_rast

FROM aerials.bostonWHERE

ST_Intersects(rast,ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, ←↩

-71.1210, 42.218,4326),26986) )";command = new NpgsqlCommand(sql, conn);

command.Parameters.Add(new NpgsqlParameter("input_srid", input_srid));

result = (byte[]) command.ExecuteScalar();conn.Close();

}

}catch (Exception ex){

result = null;context.Response.Write(ex.Message.Trim());

}return result;

}}

5.3.3 Java console app that outputs raster query as Image file

This is a simple java console app that takes a query that returns one image and outputs to specified file.

You can download the latest PostgreSQL JDBC drivers from http://jdbc.postgresql.org/download.html

You can compile the following code using a command something like:

set env CLASSPATH .:..\postgresql-9.0-801.jdbc4.jar

http://jdbc.postgresql.org/download.html


javac SaveQueryImage.javajar cfm SaveQueryImage.jar Manifest.txt *.class

And call it from the command-line with something like

java -jar SaveQueryImage.jar "SELECT ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),10, ’ ←↩quad_segs=2’),150, 150, ’8BUI’,100));" "test.png"

-- Manifest.txt --Class-Path: postgresql-9.0-801.jdbc4.jarMain-Class: SaveQueryImage

// Code for SaveQueryImage.javaimport java.sql.Connection;import java.sql.SQLException;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.io.*;

public class SaveQueryImage {public static void main(String[] argv) {

System.out.println("Checking if Driver is registered with DriverManager.");

try {//java.sql.DriverManager.registerDriver (new org.postgresql.Driver());Class.forName("org.postgresql.Driver");

}catch (ClassNotFoundException cnfe) {

System.out.println("Couldn’t find the driver!");cnfe.printStackTrace();System.exit(1);

}

Connection conn = null;

try {conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/mydb","myuser ←↩

", "mypwd");conn.setAutoCommit(false);

PreparedStatement sGetImg = conn.prepareStatement(argv[0]);

ResultSet rs = sGetImg.executeQuery();

FileOutputStream fout;try{

rs.next();/** Output to file name requested by user **/fout = new FileOutputStream(new File(argv[1]) );fout.write(rs.getBytes(1));fout.close();

}catch(Exception e){

System.out.println("Can’t create file");e.printStackTrace();

}

rs.close();sGetImg.close();


conn.close();}catch (SQLException se) {

System.out.println("Couldn’t connect: print out a stack trace and exit.");se.printStackTrace();System.exit(1);

}}

}

5.3.4 Use PLPython to dump out images via SQL

This is a plpython stored function that creates a file in the server directory for each record.

//plpython postgresql stored proc. Requires you have plpython installedCREATE OR REPLACE FUNCTION write_file (param_bytes bytea, param_filepath text)RETURNS textAS $$f = open(param_filepath, ’wb+’)f.write(param_bytes)return param_filepath$$ LANGUAGE plpythonu;

--write out 5 images to the PostgreSQL server in varying sizes-- note the postgresql daemon account needs to have write access to folder-- this echos back the file names created;SELECT write_file(ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),j*5, ’quad_segs=2’),150*j, 150*j, ’8BUI’,100)),’C:/temp/slices’|| j || ’.png’)FROM generate_series(1,5) As j;

write_file---------------------C:/temp/slices1.pngC:/temp/slices2.pngC:/temp/slices3.pngC:/temp/slices4.pngC:/temp/slices5.png

5.3.5 Outputting Rasters with PSQL

Sadly PSQL doesn’t have easy to use built-in functionality for outputting binaries. This is a bit of a hack and based on one of thesuggestions outlined in Clever Trick Challenge -- Outputting bytea with psql that piggy backs on PostgreSQL somewhat legacylarge object support. To use first launch your psql commandline connected to your database.

Unlike the python approach, this approach creates the file on your local computer.

SELECT oid, lowrite(lo_open(oid, 131072), png) As num_bytesFROM( VALUES (lo_create(0),ST_AsPNG( (SELECT rast FROM aerials.boston WHERE rid=1) )

) ) As v(oid,png);-- you’ll get an output something like --

oid | num_bytes---------+-----------2630819 | 74860

-- next note the oid and do this replacing the c:/test.png to file path location

http://people.planetpostgresql.org/andrew/index.php?/archives/196-Clever-trick-challenge.html


-- on your local computer\lo_export 2630819 ’C:/temp/aerial_samp.png’

-- this deletes the file from large object storage on dbSELECT lo_unlink(2630819);


Chapter 6

Using PostGIS Geometry: Building Applications

6.1 Using MapServer

The Minnesota MapServer is an internet web-mapping server which conforms to the OpenGIS Web Mapping Server specification.

• The MapServer homepage is at http://mapserver.org.

• The OpenGIS Web Map Specification is at http://www.opengeospatial.org/standards/wms.

6.1.1 Basic Usage

To use PostGIS with MapServer, you will need to know about how to configure MapServer, which is beyond the scope of thisdocumentation. This section will cover specific PostGIS issues and configuration details.

To use PostGIS with MapServer, you will need:

• Version 0.6 or newer of PostGIS.

• Version 3.5 or newer of MapServer.

MapServer accesses PostGIS/PostgreSQL data like any other PostgreSQL client -- using the libpq interface. This means thatMapServer can be installed on any machine with network access to the PostGIS server, and use PostGIS as a source of data. Thefaster the connection between the systems, the better.

1. Compile and install MapServer, with whatever options you desire, including the "--with-postgis" configuration option.

2. In your MapServer map file, add a PostGIS layer. For example:

LAYERCONNECTIONTYPE postgisNAME "widehighways"# Connect to a remote spatial databaseCONNECTION "user=dbuser dbname=gisdatabase host=bigserver"PROCESSING "CLOSE_CONNECTION=DEFER"# Get the lines from the ’geom’ column of the ’roads’ tableDATA "geom from roads using srid=4326 using unique gid"STATUS ONTYPE LINE# Of the lines in the extents, only render the wide highwaysFILTER "type = ’highway’ and numlanes >= 4"CLASS

# Make the superhighways brighter and 2 pixels wide

http://mapserver.org

http://www.opengeospatial.org/standards/wms


EXPRESSION ([numlanes] >= 6)STYLECOLOR 255 22 22WIDTH 2

ENDENDCLASS

# All the rest are darker and only 1 pixel wideEXPRESSION ([numlanes] < 6)STYLECOLOR 205 92 82

ENDEND

END

In the example above, the PostGIS-specific directives are as follows:

CONNECTIONTYPE For PostGIS layers, this is always "postgis".

CONNECTION The database connection is governed by the a ’connection string’ which is a standard set of keys andvalues like this (with the default values in <>):user=<username> password=<password> dbname=<username> hostname=<server> port=<5432>An empty connection string is still valid, and any of the key/value pairs can be omitted. At a minimum you willgenerally supply the database name and username to connect with.

DATA The form of this parameter is "<geocolumn> from <tablename> using srid=<srid> using unique <primary key>"where the column is the spatial column to be rendered to the map, the SRID is SRID used by the column and theprimary key is the table primary key (or any other uniquely-valued column with an index).You can omit the "using srid" and "using unique" clauses and MapServer will automatically determine the correctvalues if possible, but at the cost of running a few extra queries on the server for each map draw.

PROCESSING Putting in a CLOSE_CONNECTION=DEFER if you have multiple layers reuses existing connectionsinstead of closing them. This improves speed. Refer to for MapServer PostGIS Performance Tips for a more detailedexplanation.

FILTER The filter must be a valid SQL string corresponding to the logic normally following the "WHERE" keyword ina SQL query. So, for example, to render only roads with 6 or more lanes, use a filter of "num_lanes >= 6".

3. In your spatial database, ensure you have spatial (GiST) indexes built for any the layers you will be drawing.

CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometrycolumn] );

4. If you will be querying your layers using MapServer you will also need to use the "using unique" clause in your DATAstatement.

MapServer requires unique identifiers for each spatial record when doing queries, and the PostGIS module of MapServeruses the unique value you specify in order to provide these unique identifiers. Using the table primary key is the bestpractice.

6.1.2 Frequently Asked Questions

1. When I use an EXPRESSION in my map file, the condition never returns as true, even though I know the values exist inmy table.

Unlike shape files, PostGIS field names have to be referenced in EXPRESSIONS using lower case.

EXPRESSION ([numlanes] >= 6)

2. The FILTER I use for my Shape files is not working for my PostGIS table of the same data.

Unlike shape files, filters for PostGIS layers use SQL syntax (they are appended to the SQL statement the PostGIS con-nector generates for drawing layers in MapServer).

http://blog.cleverelephant.ca/2008/10/mapserverpostgis-performance-tips.html


FILTER "type = ’highway’ and numlanes >= 4"

3. My PostGIS layer draws much slower than my Shape file layer, is this normal?

In general, the more features you are drawing into a given map, the more likely it is that PostGIS will be slower thanShape files. For maps with relatively few features (100s), PostGIS will often be faster. For maps with high feature density(1000s), PostGIS will always be slower. If you are finding substantial draw performance problems, it is possible that youhave not built a spatial index on your table.

postgis# CREATE INDEX geotable_gix ON geotable USING GIST ( geocolumn );postgis# VACUUM ANALYZE;

4. My PostGIS layer draws fine, but queries are really slow. What is wrong?

For queries to be fast, you must have a unique key for your spatial table and you must have an index on that unique key.Youcan specify what unique key for mapserver to use with the USING UNIQUE clause in your DATA line:

DATA "geom FROM geotable USING UNIQUE gid"

5. Can I use "geography" columns (new in PostGIS 1.5) as a source for MapServer layers?

Yes! MapServer understands geography columns as being the same as geometry columns, but always using an SRID of4326. Just make sure to include a "using srid=4326" clause in your DATA statement. Everything else works exactly thesame as with geometry.

DATA "geog FROM geogtable USING SRID=4326 USING UNIQUE gid"

6.1.3 Advanced Usage

The USING pseudo-SQL clause is used to add some information to help mapserver understand the results of more complexqueries. More specifically, when either a view or a subselect is used as the source table (the thing to the right of "FROM" in aDATA definition) it is more difficult for mapserver to automatically determine a unique identifier for each row and also the SRIDfor the table. The USING clause can provide mapserver with these two pieces of information as follows:

DATA "geom FROM (SELECTtable1.geom AS geom,table1.gid AS gid,table2.data AS data

FROM table1LEFT JOIN table2ON table1.id = table2.id

) AS new_table USING UNIQUE gid USING SRID=4326"

USING UNIQUE <uniqueid> MapServer requires a unique id for each row in order to identify the row when doing mapqueries. Normally it identifies the primary key from the system tables. However, views and subselects don’t automaticallyhave an known unique column. If you want to use MapServer’s query functionality, you need to ensure your view orsubselect includes a uniquely valued column, and declare it with USING UNIQUE. For example, you could explicitlyselect nee of the table’s primary key values for this purpose, or any other column which is guaranteed to be unique for theresult set.

Note"Querying a Map" is the action of clicking on a map to ask for information about the map features in that location.Don’t confuse "map queries" with the SQL query in a DATA definition.

USING SRID=<srid> PostGIS needs to know which spatial referencing system is being used by the geometries in order toreturn the correct data back to MapServer. Normally it is possible to find this information in the "geometry_columns" tablein the PostGIS database, however, this is not possible for tables which are created on the fly such as subselects and views.So the USING SRID= option allows the correct SRID to be specified in the DATA definition.


6.1.4 Examples

Lets start with a simple example and work our way up. Consider the following MapServer layer definition:

LAYERCONNECTIONTYPE postgisNAME "roads"CONNECTION "user=theuser password=thepass dbname=thedb host=theserver"DATA "geom from roads"STATUS ONTYPE LINECLASSSTYLE

COLOR 0 0 0END

ENDEND

This layer will display all the road geometries in the roads table as black lines.

Now lets say we want to show only the highways until we get zoomed in to at least a 1:100000 scale - the next two layers willachieve this effect:

LAYERCONNECTIONTYPE postgisCONNECTION "user=theuser password=thepass dbname=thedb host=theserver"PROCESSING "CLOSE_CONNECTION=DEFER"DATA "geom from roads"MINSCALE 100000STATUS ONTYPE LINEFILTER "road_type = ’highway’"CLASSCOLOR 0 0 0

ENDENDLAYER

CONNECTIONTYPE postgisCONNECTION "user=theuser password=thepass dbname=thedb host=theserver"PROCESSING "CLOSE_CONNECTION=DEFER"DATA "geom from roads"MAXSCALE 100000STATUS ONTYPE LINECLASSITEM road_typeCLASSEXPRESSION "highway"STYLE

WIDTH 2COLOR 255 0 0

ENDENDCLASSSTYLE

COLOR 0 0 0END

ENDEND

The first layer is used when the scale is greater than 1:100000, and displays only the roads of type "highway" as black lines. TheFILTER option causes only roads of type "highway" to be displayed.


The second layer is used when the scale is less than 1:100000, and will display highways as double-thick red lines, and otherroads as regular black lines.

So, we have done a couple of interesting things using only MapServer functionality, but our DATA SQL statement has remainedsimple. Suppose that the name of the road is stored in another table (for whatever reason) and we need to do a join to get it andlabel our roads.

LAYERCONNECTIONTYPE postgisCONNECTION "user=theuser password=thepass dbname=thedb host=theserver"DATA "geom FROM (SELECT roads.gid AS gid, roads.geom AS geom,

road_names.name as name FROM roads LEFT JOIN road_names ONroads.road_name_id = road_names.road_name_id)AS named_roads USING UNIQUE gid USING SRID=4326"

MAXSCALE 20000STATUS ONTYPE ANNOTATIONLABELITEM nameCLASSLABEL

ANGLE autoSIZE 8COLOR 0 192 0TYPE truetypeFONT arial

ENDEND

END

This annotation layer adds green labels to all the roads when the scale gets down to 1:20000 or less. It also demonstrates how touse an SQL join in a DATA definition.

6.2 Java Clients (JDBC)

Java clients can access PostGIS "geometry" objects in the PostgreSQL database either directly as text representations or usingthe JDBC extension objects bundled with PostGIS. In order to use the extension objects, the "postgis.jar" file must be in yourCLASSPATH along with the "postgresql.jar" JDBC driver package.

import java.sql.*;import java.util.*;import java.lang.*;import org.postgis.*;

public class JavaGIS {

public static void main(String[] args) {

java.sql.Connection conn;

try {/** Load the JDBC driver and establish a connection.

*/Class.forName("org.postgresql.Driver");String url = "jdbc:postgresql://localhost:5432/database";conn = DriverManager.getConnection(url, "postgres", "");/** Add the geometry types to the connection. Note that you

* must cast the connection to the pgsql-specific connection

* implementation before calling the addDataType() method.


*/((org.postgresql.PGConnection)conn).addDataType("geometry",Class.forName("org.postgis. ←↩

PGgeometry"));((org.postgresql.PGConnection)conn).addDataType("box3d",Class.forName("org.postgis. ←↩

PGbox3d"));/** Create a statement and execute a select query.

*/Statement s = conn.createStatement();ResultSet r = s.executeQuery("select geom,id from geomtable");while( r.next() ) {

/** Retrieve the geometry as an object then cast it to the geometry type.

* Print things out.

*/PGgeometry geom = (PGgeometry)r.getObject(1);int id = r.getInt(2);System.out.println("Row " + id + ":");System.out.println(geom.toString());

}s.close();conn.close();

}catch( Exception e ) {

e.printStackTrace();}

}}

The "PGgeometry" object is a wrapper object which contains a specific topological geometry object (subclasses of the abstractclass "Geometry") depending on the type: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon.

PGgeometry geom = (PGgeometry)r.getObject(1);if( geom.getType() == Geometry.POLYGON ) {

Polygon pl = (Polygon)geom.getGeometry();for( int r = 0; r < pl.numRings(); r++) {LinearRing rng = pl.getRing(r);System.out.println("Ring: " + r);for( int p = 0; p < rng.numPoints(); p++ ) {

Point pt = rng.getPoint(p);System.out.println("Point: " + p);System.out.println(pt.toString());

}}

}

The JavaDoc for the extension objects provides a reference for the various data accessor functions in the geometric objects.

6.3 C Clients (libpq)

...

6.3.1 Text Cursors

...

6.3.2 Binary Cursors

...


Chapter 7

Performance tips

7.1 Small tables of large geometries

7.1.1 Problem description

Current PostgreSQL versions (including 8.0) suffer from a query optimizer weakness regarding TOAST tables. TOAST tablesare a kind of "extension room" used to store large (in the sense of data size) values that do not fit into normal data pages (like longtexts, images or complex geometries with lots of vertices), see the PostgreSQL Documentation for TOAST for more information).

The problem appears if you happen to have a table with rather large geometries, but not too much rows of them (like a tablecontaining the boundaries of all European countries in high resolution). Then the table itself is small, but it uses lots of TOASTspace. In our example case, the table itself had about 80 rows and used only 3 data pages, but the TOAST table used 8225 pages.

Now issue a query where you use the geometry operator && to search for a bounding box that matches only very few of thoserows. Now the query optimizer sees that the table has only 3 pages and 80 rows. He estimates that a sequential scan on such asmall table is much faster than using an index. And so he decides to ignore the GIST index. Usually, this estimation is correct.But in our case, the && operator has to fetch every geometry from disk to compare the bounding boxes, thus reading all TOASTpages, too.

To see whether your suffer from this bug, use the "EXPLAIN ANALYZE" postgresql command. For more information andthe technical details, you can read the thread on the postgres performance mailing list: http://archives.postgresql.org/pgsql-performance/2005-02/msg00030.php

7.1.2 Workarounds

The PostgreSQL people are trying to solve this issue by making the query estimation TOAST-aware. For now, here are twoworkarounds:

The first workaround is to force the query planner to use the index. Send "SET enable_seqscan TO off;" to the server beforeissuing the query. This basically forces the query planner to avoid sequential scans whenever possible. So it uses the GIST indexas usual. But this flag has to be set on every connection, and it causes the query planner to make misestimations in other cases,so you should "SET enable_seqscan TO on;" after the query.

The second workaround is to make the sequential scan as fast as the query planner thinks. This can be achieved by creating anadditional column that "caches" the bbox, and matching against this. In our example, the commands are like:

SELECT AddGeometryColumn(’myschema’,’mytable’,’bbox’,’4326’,’GEOMETRY’,’2’);UPDATE mytable SET bbox = ST_Envelope(ST_Force_2d(the_geom));

Now change your query to use the && operator against bbox instead of geom_column, like:

SELECT geom_columnFROM mytableWHERE bbox && ST_SetSRID(’BOX3D(0 0,1 1)’::box3d,4326);

http://www.postgresql.org/docs/current/static/storage-toast.html


Of course, if you change or add rows to mytable, you have to keep the bbox "in sync". The most transparent way to do this wouldbe triggers, but you also can modify your application to keep the bbox column current or run the UPDATE query above afterevery modification.

7.2 CLUSTERing on geometry indices

For tables that are mostly read-only, and where a single index is used for the majority of queries, PostgreSQL offers the CLUS-TER command. This command physically reorders all the data rows in the same order as the index criteria, yielding twoperformance advantages: First, for index range scans, the number of seeks on the data table is drastically reduced. Second, ifyour working set concentrates to some small intervals on the indices, you have a more efficient caching because the data rowsare spread along fewer data pages. (Feel invited to read the CLUSTER command documentation from the PostgreSQL manualat this point.)

However, currently PostgreSQL does not allow clustering on PostGIS GIST indices because GIST indices simply ignores NULLvalues, you get an error message like:

lwgeom=# CLUSTER my_geom_index ON my_table;ERROR: cannot cluster when index access method does not handle null valuesHINT: You may be able to work around this by marking column "the_geom" NOT NULL.

As the HINT message tells you, one can work around this deficiency by adding a "not null" constraint to the table:

lwgeom=# ALTER TABLE my_table ALTER COLUMN the_geom SET not null;ALTER TABLE

Of course, this will not work if you in fact need NULL values in your geometry column. Additionally, you must use the abovemethod to add the constraint, using a CHECK constraint like "ALTER TABLE blubb ADD CHECK (geometry is not null);" willnot work.

7.3 Avoiding dimension conversion

Sometimes, you happen to have 3D or 4D data in your table, but always access it using OpenGIS compliant ST_AsText() orST_AsBinary() functions that only output 2D geometries. They do this by internally calling the ST_Force_2d() function, whichintroduces a significant overhead for large geometries. To avoid this overhead, it may be feasible to pre-drop those additionaldimensions once and forever:

UPDATE mytable SET the_geom = ST_Force_2d(the_geom);VACUUM FULL ANALYZE mytable;

Note that if you added your geometry column using AddGeometryColumn() there’ll be a constraint on geometry dimension. Tobypass it you will need to drop the constraint. Remember to update the entry in the geometry_columns table and recreate theconstraint afterwards.

In case of large tables, it may be wise to divide this UPDATE into smaller portions by constraining the UPDATE to a part of thetable via a WHERE clause and your primary key or another feasible criteria, and running a simple "VACUUM;" between yourUPDATEs. This drastically reduces the need for temporary disk space. Additionally, if you have mixed dimension geometries,restricting the UPDATE by "WHERE dimension(the_geom)>2" skips re-writing of geometries that already are in 2D.

7.4 Tuning your configuration

These tips are taken from Kevin Neufeld’s presentation "Tips for the PostGIS Power User" at the FOSS4G 2007 conference.Depending on your use of PostGIS (for example, static data and complex analysis vs frequently updated data and lots of users)these changes can provide significant speedups to your queries.

For a more tips (and better formatting), the original presentation is at http://2007.foss4g.org/presentations/view.php?abstract_id=117.

http://2007.foss4g.org/presentations/view.php?abstract_id=117


7.4.1 Startup

These settings are configured in postgresql.conf:

checkpoint_segments

• Maximum number of log file segments between automatic WAL checkpoints (each segment is normally 16MB); default is 3

• Set to at least 10 or 30 for databases with heavy write activity, or more for large database loads. Another article on the topicworth reading Greg Smith: Checkpoint and Background writer

• Possibly store the xlog on a separate disk device

constraint_exclusion

• Default: off (prior to PostgreSQL 8.4 and for PostgreSQL 8.4+ is set to partition)

• This is generally used for table partitioning. If you are running PostgreSQL versions below 8.4, set to "on" to ensure the queryplanner will optimize as desired. As of PostgreSQL 8.4, the default for this is set to "partition" which is ideal for PostgreSQL8.4 and above since it will force the planner to only analyze tables for constraint consideration if they are in an inheritedhierarchy and not pay the planner penalty otherwise.

shared_buffers

• Default: ~32MB

• Set to about 1/3 to 3/4 of available RAM

7.4.2 Runtime

work_mem (the memory used for sort operations and complex queries)

• Default: 1MB

• Adjust up for large dbs, complex queries, lots of RAM

• Adjust down for many concurrent users or low RAM.

• If you have lots of RAM and few developers:

SET work_mem TO 1200000;

maintenance_work_mem (used for VACUUM, CREATE INDEX, etc.)

• Default: 16MB

• Generally too low - ties up I/O, locks objects while swapping memory

• Recommend 32MB to 256MB on production servers w/lots of RAM, but depends on the # of concurrent users. If you havelots of RAM and few developers:

SET maintainence_work_mem TO 1200000;

http://www.postgresql.org/docs/current/static/runtime-config-wal.html#GUC-CHECKPOINT-SEGMENTS

http://www.westnet.com/~gsmith/content/postgresql/chkp-bgw-83.htm

http://www.postgresql.org/docs/current/static/runtime-config-query.html#GUC-CONSTRAINT-EXCLUSION

http://www.postgresql.org/docs/current/static/runtime-config-resource.html#GUC-SHARED-BUFFERS

http://www.postgresql.org/docs/current/static/runtime-config-resource.html#GUC-WORK-MEM

http://www.postgresql.org/docs/current/static/runtime-config-resource.html#GUC-MAINTENANCE-WORK-MEM


Chapter 8

PostGIS Reference

The functions given below are the ones which a user of PostGIS is likely to need. There are other functions which are requiredsupport functions to the PostGIS objects which are not of use to a general user.

NotePostGIS has begun a transition from the existing naming convention to an SQL-MM-centric convention. As a result,most of the functions that you know and love have been renamed using the standard spatial type (ST) prefix. Previousfunctions are still available, though are not listed in this document where updated functions are equivalent. The nonST_ functions not listed in this documentation are deprecated and will be removed in a future release so STOP USINGTHEM.

8.1 PostgreSQL PostGIS Geometry/Geography/Box Types

8.1.1 box2d

box2d — A box composed of x min, ymin, xmax, ymax. Often used to return the 2d enclosing box of a geometry.

Description

box2d is a spatial data type used to represent the enclosing box of a geometry or set of geometries. ST_Extent in earlier versionsprior to PostGIS 1.4 would return a box2d.

8.1.2 box3d

box3d — A box composed of x min, ymin, zmin, xmax, ymax, zmax. Often used to return the 3d extent of a geometry orcollection of geometries.

Description

box3d is a postgis spatial data type used to represent the enclosing box of a geometry or set of geometries. ST_3DExtent returnsa box3d object.

Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type


Cast To Behaviorbox automaticbox2d automaticgeometry automatic

8.1.3 geometry

geometry — Planar spatial data type.

Description

geometry is a fundamental postgis spatial data type used to represent a feature in the Euclidean coordinate system.

Casting Behavior


Cast To Behaviorbox automaticbox2d automaticbox3d automaticbytea automaticgeography automatictext automatic

See Also

Section 4.1

8.1.4 geometry_dump

geometry_dump — A spatial datatype with two fields - geom (holding a geometry object) and path[] (a 1-d array holding theposition of the geometry within the dumped object.)

Description

geometry_dump is a compound data type consisting of a geometry object referenced by the .geom field and path[] a 1-dimensionalinteger array (starting at 1 e.g. path[1] to get first element) array that defines the navigation path within the dumped geometry tofind this element. It is used by the ST_Dump* family of functions as an output type to explode a more complex geometry intoits constituent parts and location of parts.

See Also

Section 13.5

8.1.5 geography

geography — Ellipsoidal spatial data type.


Description

geography is a spatial data type used to represent a feature in the round-earth coordinate system.

Casting Behavior


Cast To Behaviorgeometry explicit

See Also

Section 13.3, Section 4.2

8.2 Management Functions

8.2.1 AddGeometryColumn

AddGeometryColumn — Adds a geometry column to an existing table of attributes. By default uses type modifier to definerather than constraints. Pass in false for use_typmod to get old check constraint based behavior

Synopsis

text AddGeometryColumn(varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, booleanuse_typmod=true);text AddGeometryColumn(varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, inte-ger dimension, boolean use_typmod=true);text AddGeometryColumn(varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integersrid, varchar type, integer dimension, boolean use_typmod=true);

Description

Adds a geometry column to an existing table of attributes. The schema_name is the name of the table schema. The sridmust be an integer value reference to an entry in the SPATIAL_REF_SYS table. The type must be a string corresponding to thegeometry type, eg, ’POLYGON’ or ’MULTILINESTRING’ . An error is thrown if the schemaname doesn’t exist (or not visiblein the current search_path) or the specified SRID, geometry type, or dimension is invalid.

NoteChanged: 2.0.0 This function no longer updates geometry_columns since geometry_columns is a view that reads fromsystem catalogs. It by default also does not create constraints, but instead uses the built in type modifier behavior ofPostgreSQL. So for example building a wgs84 POINT column with this function is now equivalent to: ALTER TABLEsome_table ADD COLUMN geom geometry(Point,4326);Changed: 2.0.0 If you require the old behavior of constraints use the default use_typmod, but set it to false.

NoteChanged: 2.0.0 Views can no longer be manually registered in geometry_columns, however views built against geome-try typmod tables geometries and used without wrapper functions will register themselves correctly because they inheritthe typmod behavior of their parent table column. Views that use geometry functions that output other geometries willneed to be cast to typmod geometries for these view geometry columns to be registered correctly in geometry_columns.Refer to Section 4.3.4.


This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Enhanced: 2.0.0 use_typmod argument introduced. Defaults to creating typmod geometry column instead of constraint-based.

Examples

-- Create schema to hold dataCREATE SCHEMA my_schema;-- Create a new simple PostgreSQL tableCREATE TABLE my_schema.my_spatial_table (id serial);

-- Describing the table shows a simple table with a single "id" column.postgis=# \d my_schema.my_spatial_table

Table "my_schema.my_spatial_table"Column | Type | Modifiers

--------+---------+------------------------------------------------------------------------- ←↩

id | integer | not null default nextval(’my_schema.my_spatial_table_id_seq’::regclass)

-- Add a spatial column to the tableSELECT AddGeometryColumn (’my_schema’,’my_spatial_table’,’geom’,4326,’POINT’,2);

-- Add a point using the old constraint based behaviorSELECT AddGeometryColumn (’my_schema’,’my_spatial_table’,’geom_c’,4326,’POINT’,2, false);

--Add a curvepolygon using old constraint behaviorSELECT AddGeometryColumn (’my_schema’,’my_spatial_table’,’geomcp_c’,4326,’CURVEPOLYGON’,2, ←↩

false);

-- Describe the table again reveals the addition of a new geometry columns.\d my_schema.my_spatial_table

addgeometrycolumn-------------------------------------------------------------------------my_schema.my_spatial_table.geomcp_c SRID:4326 TYPE:CURVEPOLYGON DIMS:2

(1 row)

Table "my_schema.my_spatial_table"Column | Type | Modifiers

----------+----------------------+------------------------------------------------------------------------- ←↩

id | integer | not null default nextval(’my_schema. ←↩my_spatial_table_id_seq’::regclass)

geom | geometry(Point,4326) |geom_c | geometry |geomcp_c | geometry |

Check constraints:"enforce_dims_geom_c" CHECK (st_ndims(geom_c) = 2)"enforce_dims_geomcp_c" CHECK (st_ndims(geomcp_c) = 2)"enforce_geotype_geom_c" CHECK (geometrytype(geom_c) = ’POINT’::text OR geom_c IS NULL)"enforce_geotype_geomcp_c" CHECK (geometrytype(geomcp_c) = ’CURVEPOLYGON’::text OR ←↩

geomcp_c IS NULL)"enforce_srid_geom_c" CHECK (st_srid(geom_c) = 4326)"enforce_srid_geomcp_c" CHECK (st_srid(geomcp_c) = 4326)

-- geometry_columns view also registers the new columns --



SELECT f_geometry_column As col_name, type, srid, coord_dimension As ndimsFROM geometry_columnsWHERE f_table_name = ’my_spatial_table’ AND f_table_schema = ’my_schema’;

col_name | type | srid | ndims----------+--------------+------+-------geom | Point | 4326 | 2geom_c | Point | 4326 | 2geomcp_c | CurvePolygon | 4326 | 2

See Also

DropGeometryColumn, DropGeometryTable, Section 4.3.2, Section 4.3.4

8.2.2 DropGeometryColumn

DropGeometryColumn — Removes a geometry column from a spatial table.

Synopsis

text DropGeometryColumn(varchar table_name, varchar column_name);text DropGeometryColumn(varchar schema_name, varchar table_name, varchar column_name);text DropGeometryColumn(varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name);

Description

Removes a geometry column from a spatial table. Note that schema_name will need to match the f_table_schema field of thetable’s row in the geometry_columns table.




NoteChanged: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a viewagainst the system catalogs, you can drop a geometry column like any other table column using ALTER TABLE

Examples

SELECT DropGeometryColumn (’my_schema’,’my_spatial_table’,’geom’);----RESULT output ---

dropgeometrycolumn------------------------------------------------------my_schema.my_spatial_table.geom effectively removed.

-- In PostGIS 2.0+ the above is also equivalent to the standard-- the standard alter table. Both will deregister from geometry_columnsALTER TABLE my_schema.my_spatial_table DROP column geom;



See Also

AddGeometryColumn, DropGeometryTable, Section 4.3.2

8.2.3 DropGeometryTable

DropGeometryTable — Drops a table and all its references in geometry_columns.

Synopsis

boolean DropGeometryTable(varchar table_name);boolean DropGeometryTable(varchar schema_name, varchar table_name);boolean DropGeometryTable(varchar catalog_name, varchar schema_name, varchar table_name);

Description

Drops a table and all its references in geometry_columns. Note: uses current_schema() on schema-aware pgsql installations ifschema is not provided.

NoteChanged: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a viewagainst the system catalogs, you can drop a table with geometry columns like any other table using DROP TABLE

Examples

SELECT DropGeometryTable (’my_schema’,’my_spatial_table’);----RESULT output ---my_schema.my_spatial_table dropped.

-- The above is now equivalent to --DROP TABLE my_schema.my_spatial_table;

See Also

AddGeometryColumn, DropGeometryColumn, Section 4.3.2

8.2.4 PostGIS_Full_Version

PostGIS_Full_Version — Reports full postgis version and build configuration infos.

Synopsis

text PostGIS_Full_Version();

Description

Reports full postgis version and build configuration infos. Also informs about synchronization between libraries and scriptssuggesting upgrades as needed.


Examples

SELECT PostGIS_Full_Version();postgis_full_version

----------------------------------------------------------------------------------POSTGIS="1.3.3" GEOS="3.1.0-CAPI-1.5.0" PROJ="Rel. 4.4.9, 29 Oct 2004" USE_STATS

(1 row)

See Also

Section 2.9, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

8.2.5 PostGIS_GEOS_Version

PostGIS_GEOS_Version — Returns the version number of the GEOS library.

Synopsis

text PostGIS_GEOS_Version();

Description

Returns the version number of the GEOS library, or NULL if GEOS support is not enabled.

Examples

SELECT PostGIS_GEOS_Version();postgis_geos_version

----------------------3.1.0-CAPI-1.5.0

(1 row)

See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

8.2.6 PostGIS_LibXML_Version

PostGIS_LibXML_Version — Returns the version number of the libxml2 library.

Synopsis

text PostGIS_LibXML_Version();

Description

Returns the version number of the LibXML2 library.

Availability: 1.5


Examples

SELECT PostGIS_LibXML_Version();postgis_libxml_version

----------------------2.7.6

(1 row)

See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_PROJ_Version, PostGIS_GEOS_Version, PostGIS_Version

8.2.7 PostGIS_Lib_Build_Date

PostGIS_Lib_Build_Date — Returns build date of the PostGIS library.

Synopsis

text PostGIS_Lib_Build_Date();

Description

Returns build date of the PostGIS library.

Examples

SELECT PostGIS_Lib_Build_Date();postgis_lib_build_date

------------------------2008-06-21 17:53:21

(1 row)

8.2.8 PostGIS_Lib_Version

PostGIS_Lib_Version — Returns the version number of the PostGIS library.

Synopsis

text PostGIS_Lib_Version();

Description

Returns the version number of the PostGIS library.

Examples

SELECT PostGIS_Lib_Version();postgis_lib_version

---------------------1.3.3

(1 row)


See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

8.2.9 PostGIS_PROJ_Version

PostGIS_PROJ_Version — Returns the version number of the PROJ4 library.

Synopsis

text PostGIS_PROJ_Version();

Description

Returns the version number of the PROJ4 library, or NULL if PROJ4 support is not enabled.

Examples

SELECT PostGIS_PROJ_Version();postgis_proj_version

-------------------------Rel. 4.4.9, 29 Oct 2004

(1 row)

See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

8.2.10 PostGIS_Scripts_Build_Date

PostGIS_Scripts_Build_Date — Returns build date of the PostGIS scripts.

Synopsis

text PostGIS_Scripts_Build_Date();

Description

Returns build date of the PostGIS scripts.

Availability: 1.0.0RC1

Examples

SELECT PostGIS_Scripts_Build_Date();postgis_scripts_build_date

-------------------------2007-08-18 09:09:26

(1 row)


See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

8.2.11 PostGIS_Scripts_Installed

PostGIS_Scripts_Installed — Returns version of the postgis scripts installed in this database.

Synopsis

text PostGIS_Scripts_Installed();

Description

Returns version of the postgis scripts installed in this database.

NoteIf the output of this function doesn’t match the output of PostGIS_Scripts_Released you probably missed to properlyupgrade an existing database. See the Upgrading section for more info.

Availability: 0.9.0

Examples

SELECT PostGIS_Scripts_Installed();postgis_scripts_installed

-------------------------1.5.0SVN

(1 row)

See Also

PostGIS_Full_Version, PostGIS_Scripts_Released, PostGIS_Version

8.2.12 PostGIS_Scripts_Released

PostGIS_Scripts_Released — Returns the version number of the postgis.sql script released with the installed postgis lib.

Synopsis

text PostGIS_Scripts_Released();

Description

Returns the version number of the postgis.sql script released with the installed postgis lib.

NoteStarting with version 1.1.0 this function returns the same value of PostGIS_Lib_Version. Kept for backward compatibil-ity.

Availability: 0.9.0


Examples

SELECT PostGIS_Scripts_Released();postgis_scripts_released

-------------------------1.3.4SVN

(1 row)

See Also

PostGIS_Full_Version, PostGIS_Scripts_Installed, PostGIS_Lib_Version

8.2.13 PostGIS_Version

PostGIS_Version — Returns PostGIS version number and compile-time options.

Synopsis

text PostGIS_Version();

Description

Returns PostGIS version number and compile-time options.

Examples

SELECT PostGIS_Version();postgis_version

---------------------------------------1.3 USE_GEOS=1 USE_PROJ=1 USE_STATS=1

(1 row)

See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version

8.2.14 Populate_Geometry_Columns

Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial con-straints This ensures they will be registered correctly in geometry_columns view. By default will convert all geometrycolumns with no type modifier to ones with type modifiers. To get old behavior set use_typmod=false

Synopsis

text Populate_Geometry_Columns(boolean use_typmod=true);int Populate_Geometry_Columns(oid relation_oid, boolean use_typmod=true);


Description

Ensures geometry columns have appropriate type modifiers or spatial constraints to ensure they are registered correctly in geo-metry_columns table.

For backwards compatibility and for spatial needs such as tble inheritance where each child table may have different geometrytype, the old check constraint behavior is still supported. If you need the old behavior, you need to pass in the new optionalargument as false use_typmod=false. When this is done geometry columns will be created with no type modifiers but willhave 3 constraints defined. In particular, this means that every geometry column belonging to a table has at least three constraints:

• enforce_dims_the_geom - ensures every geometry has the same dimension (see ST_NDims)

• enforce_geotype_the_geom - ensures every geometry is of the same type (see GeometryType)

• enforce_srid_the_geom - ensures every geometry is in the same projection (see ST_SRID)

If a table oid is provided, this function tries to determine the srid, dimension, and geometry type of all geometry columns in thetable, adding constraints as necessary. If successful, an appropriate row is inserted into the geometry_columns table, otherwise,the exception is caught and an error notice is raised describing the problem.

If the oid of a view is provided, as with a table oid, this function tries to determine the srid, dimension, and type of allthe geometries in the view, inserting appropriate entries into the geometry_columns table, but nothing is done to enforceconstraints.

The parameterless variant is a simple wrapper for the parameterized variant that first truncates and repopulates the geome-try_columns table for every spatial table and view in the database, adding spatial constraints to tables where appropriate. Itreturns a summary of the number of geometry columns detected in the database and the number that were inserted into the geo-metry_columns table. The parameterized version simply returns the number of rows inserted into the geometry_columnstable.

Availability: 1.4.0

Changed: 2.0.0 By default, now uses type modifiers instead of check constraints to constrain geometry types. You can still usecheck constraint behavior instead by using the new use_typmod and setting it to false.

Enhanced: 2.0.0 use_typmod optional argument was introduced that allows controlling if columns are created with typmodi-fiers or with check constraints.

Examples

CREATE TABLE public.myspatial_table(gid serial, geom geometry);INSERT INTO myspatial_table(geom) VALUES(ST_GeomFromText(’LINESTRING(1 2, 3 4)’,4326) );-- This will now use typ modifiers. For this to work, there must exist dataSELECT Populate_Geometry_Columns(’public.myspatial_table’::regclass);

populate_geometry_columns--------------------------

1

\d myspatial_table

Table "public.myspatial_table"Column | Type | Modifiers

--------+---------------------------+--------------------------------------------------------------- ←↩

gid | integer | not null default nextval(’myspatial_table_gid_seq’:: ←↩regclass)

geom | geometry(LineString,4326) |


-- This will change the geometry columns to use constraints if they are not typmod or have ←↩constraints already.

--For this to work, there must exist dataCREATE TABLE public.myspatial_table_cs(gid serial, geom geometry);INSERT INTO myspatial_table_cs(geom) VALUES(ST_GeomFromText(’LINESTRING(1 2, 3 4)’,4326) );SELECT Populate_Geometry_Columns(’public.myspatial_table_cs’::regclass, false);populate_geometry_columns--------------------------

1\d myspatial_table_cs

Table "public.myspatial_table_cs"Column | Type | Modifiers

--------+----------+------------------------------------------------------------------gid | integer | not null default nextval(’myspatial_table_cs_gid_seq’::regclass)geom | geometry |

Check constraints:"enforce_dims_geom" CHECK (st_ndims(geom) = 2)"enforce_geotype_geom" CHECK (geometrytype(geom) = ’LINESTRING’::text OR geom IS NULL)"enforce_srid_geom" CHECK (st_srid(geom) = 4326)

8.2.15 UpdateGeometrySRID

UpdateGeometrySRID — Updates the SRID of all features in a geometry column, geometry_columns metadata and srid. If itwas enforced with constraints, the constraints will be updated with new srid constraint. If the old was enforced by type definition,the type definition will be changed.

Synopsis

text UpdateGeometrySRID(varchar table_name, varchar column_name, integer srid);text UpdateGeometrySRID(varchar schema_name, varchar table_name, varchar column_name, integer srid);text UpdateGeometrySRID(varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integersrid);

Description

Updates the SRID of all features in a geometry column, updating constraints and reference in geometry_columns. Note: usescurrent_schema() on schema-aware pgsql installations if schema is not provided.



Examples

This will change the srid of the roads table to 4326 from whatever it was before

SELECT UpdateGeometrySRID(’roads’,’geom’,4326);

The prior example is equivalent to this DDL statement

ALTER TABLE roadsALTER COLUMN geom TYPE geometry(MULTILINESTRING, 4326)USING ST_SetSRID(geom,4326);


If you got the projection wrong (or brought it in as unknown) in load and you wanted to transform to web mercator all in oneshot You can do this with DDL but there is no equivalent PostGIS management function to do so in one go.

ALTER TABLE roadsALTER COLUMN geom TYPE geometry(MULTILINESTRING, 3857) USING ST_Transform(ST_SetSRID(geom ←↩

,4326),3857) ;

See Also

ST_SetSRID , ST_Transform

8.3 Geometry Constructors

8.3.1 ST_BdPolyFromText

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Knowntext representation.

Synopsis

geometry ST_BdPolyFromText(text WKT, integer srid);

Description

Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

NoteThrows an error if WKT is not a MULTILINESTRING. Throws an error if output is a MULTIPOLYGON; useST_BdMPolyFromText in that case, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Availability: 1.1.0 - requires GEOS >= 2.1.0.

Examples

Forthcoming

See Also

ST_BuildArea, ST_BdMPolyFromText

8.3.2 ST_BdMPolyFromText

ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString textrepresentation Well-Known text representation.



Synopsis

geometry ST_BdMPolyFromText(text WKT, integer srid);

Description

Construct a Polygon given an arbitrary collection of closed linestrings, polygons, MultiLineStrings as Well-Known text repre-sentation.

NoteThrows an error if WKT is not a MULTILINESTRING. Forces MULTIPOLYGON output even when result is really onlycomposed by a single POLYGON; use ST_BdPolyFromText if you’re sure a single POLYGON will result from operation,or see ST_BuildArea() for a postgis-specific approach.



Examples

Forthcoming

See Also

ST_BuildArea, ST_BdPolyFromText

8.3.3 ST_GeogFromText

ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

Synopsis

geography ST_GeogFromText(text EWKT);

Description

Returns a geography object from the well-known text or extended well-known representation. SRID 4326 is assumed. This is analias for ST_GeographyFromText. Points are always expressed in long lat form.

Examples

--- converting lon lat coords to geographyALTER TABLE sometable ADD COLUMN geog geography(POINT,4326);UPDATE sometable SET geog = ST_GeogFromText(’SRID=4326;POINT(’ || lon || ’ ’ || lat || ’)’) ←↩

;

See Also

ST_AsText, ST_GeographyFromText



8.3.4 ST_GeographyFromText

ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

Synopsis

geography ST_GeographyFromText(text EWKT);

Description

Returns a geography object from the well-known text representation. SRID 4326 is assumed.

See Also

ST_GeogFromText, ST_AsText

8.3.5 ST_GeogFromWKB

ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extendedWell Known Binary (EWKB).

Synopsis

geography ST_GeogFromWKB(bytea geom);

Description

The ST_GeogFromWKB function, takes a well-known binary representation (WKB) of a geometry or PostGIS Extended WKBand creates an instance of the appropriate geography type. This function plays the role of the Geometry Factory in SQL.

If SRID is not specified, it defaults to 4326 (WGS 84 long lat).


Examples

--Although bytea rep contains single \, these need to be escaped when inserting into a ←↩table

SELECT ST_AsText(ST_GeogFromWKB(E’\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q ←↩

\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230 ←↩C@’)

);st_astext

------------------------------------------------------LINESTRING(-113.98 39.198,-113.981 39.195)

(1 row)

See Also

ST_GeogFromText, ST_AsBinary


8.3.6 ST_GeomCollFromText

ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not give, itdefaults to -1.

Synopsis

geometry ST_GeomCollFromText(text WKT, integer srid);geometry ST_GeomCollFromText(text WKT);

Description

Makes a collection Geometry from the Well-Known-Text (WKT) representation with the given SRID. If SRID is not give, itdefaults to -1.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a GEOMETRYCOLLECTION

NoteIf you are absolutely sure all your WKT geometries are collections, don’t use this function. It is slower thanST_GeomFromText since it adds an additional validation step.


This method implements the SQL/MM specification.

Examples

SELECT ST_GeomCollFromText(’GEOMETRYCOLLECTION(POINT(1 2),LINESTRING(1 2, 3 4))’);

See Also

ST_GeomFromText, ST_SRID

8.3.7 ST_GeomFromEWKB

ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).

Synopsis

geometry ST_GeomFromEWKB(bytea EWKB);



Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known binary (EWKT) representation.

NoteThe EWKB format is not an OGC standard, but a PostGIS specific format that includes the spatial reference system(SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.



This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Examples

line string binary rep 0f LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932) in NAD 83 long lat(4269).

NoteNOTE: Even though byte arrays are delimited with \ and may have ’, we need to escape both out with \ and ” ifstandard_conforming_strings is off. So it does not look exactly like its AsEWKB representation.

SELECT ST_GeomFromEWKB(E’\\001\\002\\000\\000 \\255\\020\\000\\000\\003\\000\\000\\000\\344 ←↩J=

\\013B\\312Q\\300n\\303(\\010\\036!E@’’\\277E’’K\\312Q\\300\\366{b\\235*!E@\\225|\\354.P\\312Q\\300p\\231\\323e1!E@’);

NoteIn PostgreSQL 9.1+ - standard_conforming_strings is set to on by default, where as in past versions it was set to on.You can change defaults as needed for a single query or at the database or server level. Below is how you would do itwith standard_conforming_strings = on. In this case we escape the ’ with standard ansi ’, but slashes are not escaped

set standard_conforming_strings = on;SELECT ST_GeomFromEWKB(’\001\002\000\000 \255\020\000\000\003\000\000\000\344J=\012\013B

\312Q\300n\303(\010\036!E@’’\277E’’K\012\312Q\300\366{b\235*!E@\225|\354.P\312Q\012\300 ←↩p\231\323e1’)

See Also

ST_AsBinary, ST_AsEWKB, ST_GeomFromWKB


8.3.8 ST_GeomFromEWKT

ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).

Synopsis

geometry ST_GeomFromEWKT(text EWKT);

Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known text (EWKT) representation.

NoteThe EWKT format is not an OGC standard, but an PostGIS specific format that includes the spatial reference system(SRID) identifier






Examples

SELECT ST_GeomFromEWKT(’SRID=4269;LINESTRING(-71.160281 42.258729,-71.160837 ←↩42.259113,-71.161144 42.25932)’);

SELECT ST_GeomFromEWKT(’SRID=4269;MULTILINESTRING((-71.160281 42.258729,-71.160837 ←↩42.259113,-71.161144 42.25932))’);

SELECT ST_GeomFromEWKT(’SRID=4269;POINT(-71.064544 42.28787)’);

SELECT ST_GeomFromEWKT(’SRID=4269;POLYGON((-71.1776585052917 ←↩42.3902909739571,-71.1776820268866 42.3903701743239,

-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 ←↩42.3902909739571))’);

SELECT ST_GeomFromEWKT(’SRID=4269;MULTIPOLYGON(((-71.1031880899493 42.3152774590236,-71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,-71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,-71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,-71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,-71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,-71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,-71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,-71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,-71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,-71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,-71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,-71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,


-71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,-71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,-71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,-71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,-71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,-71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,-71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,-71.1031880899493 42.3152774590236)),((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,-71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 ←↩

42.315113108546)))’);

--3d circular stringSELECT ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)’);

--Polyhedral Surface exampleSELECT ST_GeomFromEWKT(’POLYHEDRALSURFACE(

((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))

)’);

See Also

ST_AsEWKT, ST_GeomFromText, ST_GeomFromEWKT

8.3.9 ST_GeometryFromText

ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an aliasname for ST_GeomFromText

Synopsis

geometry ST_GeometryFromText(text WKT);geometry ST_GeometryFromText(text WKT, integer srid);

Description


This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

See Also

ST_GeomFromText

8.3.10 ST_GeomFromGML

ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object



Synopsis

geometry ST_GeomFromGML(text geomgml);geometry ST_GeomFromGML(text geomgml, integer srid);

Description

Constructs a PostGIS ST_Geometry object from the OGC GML representation.

ST_GeomFromGML works only for GML Geometry fragments. It throws an error if you try to use it on a whole GML document.

OGC GML versions supported:

• GML 3.2.1 Namespace

• GML 3.1.1 Simple Features profile SF-2 (with GML 3.1.0 and 3.0.0 backward compatibility)

• GML 2.1.2

OGC GML standards, cf: http://www.opengeospatial.org/standards/gml:

Availability: 1.5, requires libxml2 1.6+


Enhanced: 2.0.0 default srid optional parameter added.




GML allow mixed dimensions (2D and 3D inside the same MultiGeometry for instance). As PostGIS geometries don’t,ST_GeomFromGML convert the whole geometry to 2D if a missing Z dimension is found once.

GML support mixed SRS inside the same MultiGeometry. As PostGIS geometries don’t, ST_GeomFromGML, in this case,reproject all subgeometries to the SRS root node. If no srsName attribute available for the GML root node, the function throw anerror.

ST_GeomFromGML function is not pedantic about an explicit GML namespace. You could avoid to mention it explicitly forcommon usages. But you need it if you want to use XLink feature inside GML.

NoteST_GeomFromGML function not support SQL/MM curves geometries.

Examples - A single geometry with srsName

SELECT ST_GeomFromGML(’<gml:LineString srsName="EPSG:4269">

<gml:coordinates>-71.16028,42.258729 -71.160837,42.259112 -71.161143,42.25932

</gml:coordinates></gml:LineString>’);

http://www.opengeospatial.org/standards/gml


Examples - XLink usage

SELECT ST_GeomFromGML(’<gml:LineString xmlns:gml="http://www.opengis.net/gml"

xmlns:xlink="http://www.w3.org/1999/xlink"srsName="urn:ogc:def:crs:EPSG::4269">

<gml:pointProperty><gml:Point gml:id="p1"><gml:pos>42.258729 -71.16028</gml:pos></gml:Point>

</gml:pointProperty><gml:pos>42.259112 -71.160837</gml:pos><gml:pointProperty>

<gml:Point xlink:type="simple" xlink:href="#p1"/></gml:pointProperty>

</gml:LineString>’););

Examples - Polyhedral Surface

SELECT ST_AsEWKT(ST_GeomFromGML(’<gml:PolyhedralSurface><gml:polygonPatches>

<gml:PolygonPatch><gml:exterior>

<gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml: ←↩posList></gml:LinearRing>

</gml:exterior></gml:PolygonPatch><gml:PolygonPatch><gml:exterior>










</gml:exterior></gml:PolygonPatch>

</gml:polygonPatches></gml:PolyhedralSurface>’));

-- result --


POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))

See Also

Section 2.4.1, ST_AsGML, ST_GMLToSQL

8.3.11 ST_GeomFromGeoJSON

ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromGeoJSON(text geomjson);

Description

Constructs a PostGIS geometry object from the GeoJSON representation.

ST_GeomFromGeoJSON works only for JSON Geometry fragments. It throws an error if you try to use it on a whole JSONdocument.

Availability: 2.0.0 requires - JSON-C >= 0.9

NoteIf you do not have JSON-C enabled, support you will get an error notice instead of seeing an output. To enable JSON-C,run configure --with-jsondir=/path/to/json-c. See Section 2.4.1 for details.


Examples

SELECT ST_AsText(ST_GeomFromGeoJSON(’{"type":"Point","coordinates":[-48.23456,20.12345]}’)) ←↩As wkt;

wkt------POINT(-48.23456 20.12345)

-- a 3D linestringSELECT ST_AsText(ST_GeomFromGeoJSON(’{"type":"LineString","coordinates ←↩

":[[1,2,3],[4,5,6],[7,8,9]]}’)) As wkt;

wkt-------------------LINESTRING(1 2,4 5,7 8)


See Also

ST_AsText, ST_AsGeoJSON, Section 2.4.1

8.3.12 ST_GeomFromKML

ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object

Synopsis

geometry ST_GeomFromKML(text geomkml);

Description

Constructs a PostGIS ST_Geometry object from the OGC KML representation.

ST_GeomFromKML works only for KML Geometry fragments. It throws an error if you try to use it on a whole KML document.

OGC KML versions supported:

• KML 2.2.0 Namespace

OGC KML standards, cf: http://www.opengeospatial.org/standards/kml:

Availability: 1.5,libxml2 2.6+


NoteST_GeomFromKML function not support SQL/MM curves geometries.

Examples - A single geometry with srsName

SELECT ST_GeomFromKML(’<LineString>

<coordinates>-71.1663,42.2614-71.1667,42.2616</coordinates>

</LineString>’);

See Also

Section 2.4.1, ST_AsKML

8.3.13 ST_GMLToSQL

ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML

Synopsis

geometry ST_GMLToSQL(text geomgml);geometry ST_GMLToSQL(text geomgml, integer srid);

http://www.opengeospatial.org/standards/kml


Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.50 (except for curves support).

Availability: 1.5, requires libxml2 1.6+


Enhanced: 2.0.0 default srid optional parameter added.

See Also

Section 2.4.1, ST_GeomFromGML, ST_AsGML

8.3.14 ST_GeomFromText

ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).

Synopsis

geometry ST_GeomFromText(text WKT);geometry ST_GeomFromText(text WKT, integer srid);

Description

Constructs a PostGIS ST_Geometry object from the OGC Well-Known text representation.

NoteThere are 2 variants of ST_GeomFromText function, the first takes no SRID and returns a geometry with no definedspatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometrythat includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRIDis from the conformance suite.



WarningChanged: 2.0.0 In prior versions of PostGIS ST_GeomFromText(’GEOMETRYCOLLECTION(EMPTY)’) was allowed.This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written asST_GeomFromText(’GEOMETRYCOLLECTION EMPTY’)



Examples

SELECT ST_GeomFromText(’LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 ←↩42.25932)’);

SELECT ST_GeomFromText(’LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 ←↩42.25932)’,4269);

SELECT ST_GeomFromText(’MULTILINESTRING((-71.160281 42.258729,-71.160837 ←↩42.259113,-71.161144 42.25932))’);

SELECT ST_GeomFromText(’POINT(-71.064544 42.28787)’);

SELECT ST_GeomFromText(’POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 ←↩42.3903701743239,

-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 ←↩42.3902909739571))’);

SELECT ST_GeomFromText(’MULTIPOLYGON(((-71.1031880899493 42.3152774590236,-71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,-71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,-71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,-71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,-71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,-71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,-71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,-71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,-71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,-71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,-71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,-71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,-71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,-71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,-71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,-71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,-71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,-71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,-71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,-71.1031880899493 42.3152774590236)),((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,-71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 ←↩

42.315113108546)))’,4326);

SELECT ST_GeomFromText(’CIRCULARSTRING(220268 150415,220227 150505,220227 150406)’);

See Also

ST_GeomFromEWKT, ST_GeomFromWKB, ST_SRID

8.3.15 ST_GeomFromWKB

ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optionalSRID.

Synopsis

geometry ST_GeomFromWKB(bytea geom);geometry ST_GeomFromWKB(bytea geom, integer srid);


Description

The ST_GeomFromWKB function, takes a well-known binary representation of a geometry and a Spatial Reference System ID(SRID) and creates an instance of the appropriate geometry type. This function plays the role of the Geometry Factory in SQL.This is an alternate name for ST_WKBToSQL.

If SRID is not specified, it defaults to -1 (Unknown).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.7.2 - the optionalSRID is from the conformance suite



Examples

--Although bytea rep contains single \, these need to be escaped when inserting into a ←↩table-- unless standard_conforming_strings is set to on.

SELECT ST_AsEWKT(ST_GeomFromWKB(E’\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q ←↩

\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230 ←↩C@’,4326)

);st_asewkt

------------------------------------------------------SRID=4326;LINESTRING(-113.98 39.198,-113.981 39.195)

(1 row)

SELECTST_AsText(ST_GeomFromWKB(ST_AsEWKB(’POINT(2 5)’::geometry)

));

st_astext------------POINT(2 5)

(1 row)

See Also

ST_WKBToSQL, ST_AsBinary, ST_GeomFromEWKB

8.3.16 ST_LineFromMultiPoint

ST_LineFromMultiPoint — Creates a LineString from a MultiPoint geometry.

Synopsis

geometry ST_LineFromMultiPoint(geometry aMultiPoint);



Description

Creates a LineString from a MultiPoint geometry.


Examples

--Create a 3d line string from a 3d multipointSELECT ST_AsEWKT(ST_LineFromMultiPoint(ST_GeomFromEWKT(’MULTIPOINT(1 2 3, 4 5 6, 7 8 9)’))) ←↩

;--result--LINESTRING(1 2 3,4 5 6,7 8 9)

See Also

ST_AsEWKT, ST_Collect, ST_MakeLine

8.3.17 ST_LineFromText

ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to -1.

Synopsis

geometry ST_LineFromText(text WKT);geometry ST_LineFromText(text WKT, integer srid);

Description

Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. If WKT passed in is not a LINESTRING,then null is returned.

NoteOGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

NoteIf you know all your geometries are LINESTRINGS, its more efficient to just use ST_GeomFromText. This just callsST_GeomFromText and adds additional validation that it returns a linestring.





Examples

SELECT ST_LineFromText(’LINESTRING(1 2, 3 4)’) AS aline, ST_LineFromText(’POINT(1 2)’) AS ←↩null_return;

aline | null_return------------------------------------------------010200000002000000000000000000F ... | t

See Also

ST_GeomFromText

8.3.18 ST_LineFromWKB

ST_LineFromWKB — Makes a LINESTRING from WKB with the given SRID

Synopsis

geometry ST_LineFromWKB(bytea WKB);geometry ST_LineFromWKB(bytea WKB, integer srid);

Description

The ST_LineFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID(SRID) and creates an instance of the appropriate geometry type - in this case, a LINESTRING geometry. This function playsthe role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to -1. NULL is returned if the input bytea does not represent a LINESTRING.

NoteOGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

NoteIf you know all your geometries are LINESTRINGs, its more efficient to just use ST_GeomFromWKB. This functionjust calls ST_GeomFromWKB and adds additional validation that it returns a linestring.



Examples

SELECT ST_LineFromWKB(ST_AsBinary(ST_GeomFromText(’LINESTRING(1 2, 3 4)’))) AS aline,ST_LineFromWKB(ST_AsBinary(ST_GeomFromText(’POINT(1 2)’))) IS NULL AS null_return;

aline | null_return------------------------------------------------010200000002000000000000000000F ... | t



See Also

ST_GeomFromWKB, ST_LinestringFromWKB

8.3.19 ST_LinestringFromWKB

ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.

Synopsis

geometry ST_LinestringFromWKB(bytea WKB);geometry ST_LinestringFromWKB(bytea WKB, integer srid);

Description

The ST_LinestringFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference Sys-tem ID (SRID) and creates an instance of the appropriate geometry type - in this case, a LINESTRING geometry. This functionplays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to -1. NULL is returned if the input bytea does not represent a LINESTRING geometry.This an alias for ST_LineFromWKB.

NoteOGC SPEC 3.2.6.2 - optional SRID is from the conformance suite.

NoteIf you know all your geometries are LINESTRINGs, it’s more efficient to just use ST_GeomFromWKB. This functionjust calls ST_GeomFromWKB and adds additional validation that it returns a LINESTRING.



Examples

SELECTST_LineStringFromWKB(ST_AsBinary(ST_GeomFromText(’LINESTRING(1 2, 3 4)’))) AS aline,ST_LinestringFromWKB(ST_AsBinary(ST_GeomFromText(’POINT(1 2)’))) IS NULL AS null_return;aline | null_return

------------------------------------------------010200000002000000000000000000F ... | t

See Also

ST_GeomFromWKB, ST_LineFromWKB



8.3.20 ST_MakeBox2D

ST_MakeBox2D — Creates a BOX2D defined by the given point geometries.

Synopsis

box2d ST_MakeBox2D(geometry pointLowLeft, geometry pointUpRight);

Description

Creates a BOX2D defined by the given point geometries. This is useful for doing range queries

Examples

--Return all features that fall reside or partly reside in a US national atlas coordinate ←↩bounding box

--It is assumed here that the geometries are stored with SRID = 2163 (US National atlas ←↩equal area)

SELECT feature_id, feature_name, the_geomFROM featuresWHERE the_geom && ST_SetSRID(ST_MakeBox2D(ST_Point(-989502.1875, 528439.5625),

ST_Point(-987121.375 ,529933.1875)),2163)

See Also

ST_MakePoint, ST_Point, ST_SetSRID, ST_SRID

8.3.21 ST_3DMakeBox

ST_3DMakeBox — Creates a BOX3D defined by the given 3d point geometries.

Synopsis

box3d ST_3DMakeBox(geometry point3DLowLeftBottom, geometry point3DUpRightTop);

Description

Creates a BOX3D defined by the given 2 3D point geometries.


Changed: 2.0.0 In prior versions this used to be called ST_MakeBox3D

Examples

SELECT ST_3DMakeBox(ST_MakePoint(-989502.1875, 528439.5625, 10),ST_MakePoint(-987121.375 ,529933.1875, 10)) As abb3d

--bb3d----------BOX3D(-989502.1875 528439.5625 10,-987121.375 529933.1875 10)


See Also

ST_MakePoint, ST_SetSRID, ST_SRID

8.3.22 ST_MakeLine

ST_MakeLine — Creates a Linestring from point or line geometries.

Synopsis

geometry ST_MakeLine(geometry set geoms);geometry ST_MakeLine(geometry geom1, geometry geom2);geometry ST_MakeLine(geometry[] geoms_array);

Description

ST_MakeLine comes in 3 forms: a spatial aggregate that takes rows of point-or-line geometries and returns a line string, afunction that takes an array of point-or-lines, and a regular function that takes two point-or-line geometries. You might want touse a subselect to order points before feeding them to the aggregate version of this function.

When adding line components a common node is removed from the output.


Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle morepoints faster.

Availability: 2.0.0 - Support for linestring input elements was introduced

Examples: Spatial Aggregate version

This example takes a sequence of GPS points and creates one record for each gps travel where the geometry field is a line stringcomposed of the gps points in the order of the travel.

-- For pre-PostgreSQL 9.0 - this usually works,-- but the planner may on occasion choose not to respect the order of the subquerySELECT gps.gps_track, ST_MakeLine(gps.the_geom) As newgeom

FROM (SELECT gps_track,gps_time, the_geomFROM gps_points ORDER BY gps_track, gps_time) As gps

GROUP BY gps.gps_track;

-- If you are using PostgreSQL 9.0+-- (you can use the new ORDER BY support for aggregates)-- this is a guaranteed way to get a correctly ordered linestring-- Your order by part can order by more than one column if neededSELECT gps.gps_track, ST_MakeLine(gps.the_geom ORDER BY gps_time) As newgeom

FROM gps_points As gpsGROUP BY gps.gps_track;

Examples: Non-Spatial Aggregate version

First example is a simple one off line string composed of 2 points. The second formulates line strings from 2 points a user draws.The third is a one-off that joins 2 3d points to create a line in 3d space.


SELECT ST_AsText(ST_MakeLine(ST_MakePoint(1,2), ST_MakePoint(3,4)));st_astext

---------------------LINESTRING(1 2,3 4)

SELECT userpoints.id, ST_MakeLine(startpoint, endpoint) As drawn_lineFROM userpoints ;

SELECT ST_AsEWKT(ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5)));st_asewkt

-------------------------LINESTRING(1 2 3,3 4 5)

Examples: Using Array version

SELECT ST_MakeLine(ARRAY(SELECT ST_Centroid(the_geom) FROM visit_locations ORDER BY ←↩visit_time));

--Making a 3d line with 3 3-d pointsSELECT ST_AsEWKT(ST_MakeLine(ARRAY[ST_MakePoint(1,2,3),

ST_MakePoint(3,4,5), ST_MakePoint(6,6,6)]));st_asewkt

-------------------------LINESTRING(1 2 3,3 4 5,6 6 6)

See Also

ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_MakePoint

8.3.23 ST_MakeEnvelope

ST_MakeEnvelope — Creates a rectangular Polygon formed from the given minimums and maximums. Input values must be inSRS specified by the SRID.

Synopsis

geometry ST_MakeEnvelope(double precision xmin, double precision ymin, double precision xmax, double precision ymax,integer srid=unknown);

Description

Creates a rectangular Polygon formed from the minima and maxima. by the given shell. Input values must be in SRS specifiedby the SRID. If no SRID is specified the unknown spatial reference system is assumed

Availability: 1.5

Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.

Example: Building a bounding box polygon

SELECT ST_AsText(ST_MakeEnvelope(10, 10, 11, 11, 4326));

st_asewkt-----------POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))


See Also

ST_MakePoint, ST_MakeLine, ST_MakePolygon

8.3.24 ST_MakePolygon

ST_MakePolygon — Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS.

Synopsis

geometry ST_MakePolygon(geometry linestring);

geometry ST_MakePolygon(geometry outerlinestring, geometry[] interiorlinestrings);

Description

Creates a Polygon formed by the given shell. Input geometries must be closed LINESTRINGS. Comes in 2 variants.

Variant 1: takes one closed linestring.

Variant 2: Creates a Polygon formed by the given shell and array of holes. You can construct a geometry array using ST_Accumor the PostgreSQL ARRAY[] and ARRAY() constructs. Input geometries must be closed LINESTRINGS.

NoteThis function will not accept a MULTILINESTRING. Use ST_LineMerge or ST_Dump to generate line strings.


Examples: Single closed LINESTRING

--2d lineSELECT ST_MakePolygon(ST_GeomFromText(’LINESTRING(75.15 29.53,77 29,77.6 29.5, 75.15 29.53) ←↩

’));--If linestring is not closed--you can add the start point to close itSELECT ST_MakePolygon(ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)))FROM (SELECT ST_GeomFromText(’LINESTRING(75.15 29.53,77 29,77.6 29.5)’) As open_line) As foo;

--3d closed lineSELECT ST_MakePolygon(ST_GeomFromText(’LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 ←↩

29.53 1)’));

st_asewkt-----------POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

--measured line --SELECT ST_MakePolygon(ST_GeomFromText(’LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 ←↩

29.53 2)’));

st_asewkt----------POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))


Examples: Outter shell with inner shells

Build a donut with an ant hole

SELECT ST_MakePolygon(ST_ExteriorRing(ST_Buffer(foo.line,10)),

ARRAY[ST_Translate(foo.line,1,1),ST_ExteriorRing(ST_Buffer(ST_MakePoint(20,20),1)) ]

)FROM

(SELECT ST_ExteriorRing(ST_Buffer(ST_MakePoint(10,10),10,10))As line )As foo;

Build province boundaries with holes representing lakes in the province from a set of province polygons/multipolygons and waterline strings this is an example of using PostGIS ST_Accum

NoteThe use of CASE because feeding a null array into ST_MakePolygon results in NULL

Notethe use of left join to guarantee we get all provinces back even if they have no lakes

SELECT p.gid, p.province_name,CASE WHEN

ST_Accum(w.the_geom) IS NULL THEN p.the_geomELSE ST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)), ST_Accum(w.the_geom)) END

FROMprovinces p LEFT JOIN waterlines w

ON (ST_Within(w.the_geom, p.the_geom) AND ST_IsClosed(w.the_geom))GROUP BY p.gid, p.province_name, p.the_geom;

--Same example above but utilizing a correlated subquery--and PostgreSQL built-in ARRAY() function that converts a row set to an array

SELECT p.gid, p.province_name, CASE WHENEXISTS(SELECT w.the_geom

FROM waterlines wWHERE ST_Within(w.the_geom, p.the_geom)AND ST_IsClosed(w.the_geom))

THENST_MakePolygon(ST_LineMerge(ST_Boundary(p.the_geom)),

ARRAY(SELECT w.the_geomFROM waterlines wWHERE ST_Within(w.the_geom, p.the_geom)AND ST_IsClosed(w.the_geom)))

ELSE p.the_geom END As the_geomFROMprovinces p;

See Also

ST_Accum, ST_AddPoint, ST_GeometryType, ST_IsClosed, ST_LineMerge, ST_BuildArea


8.3.25 ST_MakePoint

ST_MakePoint — Creates a 2D,3DZ or 4D point geometry.

Synopsis

geometry ST_MakePoint(double precision x, double precision y);

geometry ST_MakePoint(double precision x, double precision y, double precision z);

geometry ST_MakePoint(double precision x, double precision y, double precision z, double precision m);

Description

Creates a 2D,3DZ or 4D point geometry (geometry with measure). ST_MakePointwhile not being OGC compliant is generallyfaster and more precise than ST_GeomFromText and ST_PointFromText. It is also easier to use if you have raw coordinates ratherthan WKT.

NoteNote x is longitude and y is latitude

NoteUse ST_MakePointM if you need to make a point with x,y,m.


Examples

--Return point with unknown SRIDSELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

--Return point marked as WGS 84 long latSELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

--Return a 3D point (e.g. has altitude)SELECT ST_MakePoint(1, 2,1.5);

--Get z of pointSELECT ST_Z(ST_MakePoint(1, 2,1.5));result-------1.5

See Also

ST_GeomFromText, ST_PointFromText, ST_SetSRID, ST_MakePointM

8.3.26 ST_MakePointM

ST_MakePointM — Creates a point geometry with an x y and m coordinate.


Synopsis

geometry ST_MakePointM(float x, float y, float m);

Description

Creates a point with x, y and measure coordinates.

NoteNote x is longitude and y is latitude.

Examples

We use ST_AsEWKT in these examples to show the text representation instead of ST_AsText because ST_AsText does notsupport returning M.

--Return EWKT representation of point with unknown SRIDSELECT ST_AsEWKT(ST_MakePointM(-71.1043443253471, 42.3150676015829, 10));

--resultst_asewkt

-----------------------------------------------POINTM(-71.1043443253471 42.3150676015829 10)

--Return EWKT representation of point with measure marked as WGS 84 long latSELECT ST_AsEWKT(ST_SetSRID(ST_MakePointM(-71.1043443253471, 42.3150676015829,10),4326));

st_asewkt---------------------------------------------------------SRID=4326;POINTM(-71.1043443253471 42.3150676015829 10)

--Return a 3d point (e.g. has altitude)SELECT ST_MakePoint(1, 2,1.5);

--Get m of pointSELECT ST_M(ST_MakePointM(-71.1043443253471, 42.3150676015829,10));result-------10

See Also

ST_AsEWKT, ST_MakePoint, ST_SetSRID

8.3.27 ST_MLineFromText

ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.

Synopsis

geometry ST_MLineFromText(text WKT, integer srid);geometry ST_MLineFromText(text WKT);


Description

Makes a Geometry from Well-Known-Text (WKT) with the given SRID. If SRID is not give, it defaults to -1.


Returns null if the WKT is not a MULTILINESTRING

NoteIf you are absolutely sure all your WKT geometries are points, don’t use this function. It is slower thanST_GeomFromText since it adds an additional validation step.


This method implements the SQL/MM specification.SQL-MM 3: 9.4.4

Examples

SELECT ST_MLineFromText(’MULTILINESTRING((1 2, 3 4), (4 5, 6 7))’);

See Also

ST_GeomFromText

8.3.28 ST_MPointFromText

ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

Synopsis

geometry ST_MPointFromText(text WKT, integer srid);geometry ST_MPointFromText(text WKT);

Description

Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.


Returns null if the WKT is not a MULTIPOINT

NoteIf you are absolutely sure all your WKT geometries are points, don’t use this function. It is slower thanST_GeomFromText since it adds an additional validation step.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 3.2.6.2





Examples

SELECT ST_MPointFromText(’MULTIPOINT(1 2, 3 4)’);SELECT ST_MPointFromText(’MULTIPOINT(-70.9590 42.1180, -70.9611 42.1223)’, 4326);

See Also

ST_GeomFromText

8.3.29 ST_MPolyFromText

ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

Synopsis

geometry ST_MPolyFromText(text WKT, integer srid);geometry ST_MPolyFromText(text WKT);

Description

Makes a MultiPolygon from WKT with the given SRID. If SRID is not give, it defaults to -1.


Throws an error if the WKT is not a MULTIPOLYGON

NoteIf you are absolutely sure all your WKT geometries are multipolygons, don’t use this function. It is slower thanST_GeomFromText since it adds an additional validation step.



Examples

SELECT ST_MPolyFromText(’MULTIPOLYGON(((0 0 1,20 0 1,20 20 1,0 20 1,0 0 1),(5 5 3,5 7 3,7 7 ←↩3,7 5 3,5 5 3)))’);

SELECt ST_MPolyFromText(’MULTIPOLYGON(((-70.916 42.1002,-70.9468 42.0946,-70.9765 ←↩42.0872,-70.9754 42.0875,-70.9749 42.0879,-70.9752 42.0881,-70.9754 42.0891,-70.9758 ←↩42.0894,-70.9759 42.0897,-70.9759 42.0899,-70.9754 42.0902,-70.9756 42.0906,-70.9753 ←↩42.0907,-70.9753 42.0917,-70.9757 42.0924,-70.9755 42.0928,-70.9755 42.0942,-70.9751 ←↩42.0948,-70.9755 42.0953,-70.9751 42.0958,-70.9751 42.0962,-70.9759 42.0983,-70.9767 ←↩42.0987,-70.9768 42.0991,-70.9771 42.0997,-70.9771 42.1003,-70.9768 42.1005,-70.977 ←↩42.1011,-70.9766 42.1019,-70.9768 42.1026,-70.9769 42.1033,-70.9775 42.1042,-70.9773 ←↩42.1043,-70.9776 42.1043,-70.9778 42.1048,-70.9773 42.1058,-70.9774 42.1061,-70.9779 ←↩42.1065,-70.9782 42.1078,-70.9788 42.1085,-70.9798 42.1087,-70.9806 42.109,-70.9807 ←↩42.1093,-70.9806 42.1099,-70.9809 42.1109,-70.9808 42.1112,-70.9798 42.1116,-70.9792 ←↩42.1127,-70.979 42.1129,-70.9787 42.1134,-70.979 42.1139,-70.9791 42.1141,-70.9987 ←↩42.1116,-71.0022 42.1273,

-70.9408 42.1513,-70.9315 42.1165,-70.916 42.1002)))’,4326);



See Also

ST_GeomFromText, ST_SRID

8.3.30 ST_Point

ST_Point — Returns an ST_Point with the given coordinate values. OGC alias for ST_MakePoint.

Synopsis

geometry ST_Point(float x_lon, float y_lat);

Description

Returns an ST_Point with the given coordinate values. MM compliant alias for ST_MakePoint that takes just an x and y.


Examples: Geometry

SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)

Examples: Geography

SELECT CAST(ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326) As geography);

-- the :: is PostgreSQL short-hand for casting.SELECT ST_SetSRID(ST_Point(-71.1043443253471, 42.3150676015829),4326)::geography;

--If your point coordinates are in a different spatial reference from WGS-84 long lat, then ←↩you need to transform before casting

-- This example we convert a point in Pennsylvania State Plane feet to WGS 84 and then ←↩geography

SELECT ST_Transform(ST_SetSRID(ST_Point(3637510, 3014852),2273),4326)::geography;

See Also

Section 4.2.1, ST_MakePoint, ST_SetSRID, ST_Transform

8.3.31 ST_PointFromText

ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.

Synopsis

geometry ST_PointFromText(text WKT);geometry ST_PointFromText(text WKT, integer srid);


Description

Constructs a PostGIS ST_Geometry point object from the OGC Well-Known text representation. If SRID is not give, it defaultsto unknown (currently -1). If geometry is not a WKT point representation, returns null. If completely invalid WKT, then throwsan error.

NoteThere are 2 variants of ST_PointFromText function, the first takes no SRID and returns a geometry with no definedspatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometrythat includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

NoteIf you are absolutely sure all your WKT geometries are points, don’t use this function. It is slower thanST_GeomFromText since it adds an additional validation step. If you are building points from long lat coordinatesand care more about performance and accuracy than OGC compliance, use ST_MakePoint or OGC compliant aliasST_Point.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRIDis from the conformance suite.


Examples

SELECT ST_PointFromText(’POINT(-71.064544 42.28787)’);SELECT ST_PointFromText(’POINT(-71.064544 42.28787)’, 4326);

See Also

ST_GeomFromText, ST_MakePoint, ST_Point, ST_SRID

8.3.32 ST_PointFromWKB

ST_PointFromWKB — Makes a geometry from WKB with the given SRID

Synopsis

geometry ST_GeomFromWKB(bytea geom);geometry ST_GeomFromWKB(bytea geom, integer srid);

Description

The ST_PointFromWKB function, takes a well-known binary representation of geometry and a Spatial Reference System ID(SRID) and creates an instance of the appropriate geometry type - in this case, a POINT geometry. This function plays the roleof the Geometry Factory in SQL.

If an SRID is not specified, it defaults to -1. NULL is returned if the input bytea does not represent a POINT geometry.








Examples

SELECTST_AsText(ST_PointFromWKB(ST_AsEWKB(’POINT(2 5)’::geometry)

));


(1 row)

SELECTST_AsText(ST_PointFromWKB(ST_AsEWKB(’LINESTRING(2 5, 2 6)’::geometry)

));

st_astext-----------

(1 row)

See Also

ST_GeomFromWKB, ST_LineFromWKB

8.3.33 ST_Polygon

ST_Polygon — Returns a polygon built from the specified linestring and SRID.

Synopsis

geometry ST_Polygon(geometry aLineString, integer srid);

Description

Returns a polygon built from the specified linestring and SRID.

NoteST_Polygon is similar to first version oST_MakePolygon except it also sets the spatial ref sys (SRID) of the polygon.Will not work with MULTILINESTRINGS so use LineMerge to merge multilines. Also does not create polygons withholes. Use ST_MakePolygon for that.





Examples

--a 2d polygonSELECT ST_Polygon(ST_GeomFromText(’LINESTRING(75.15 29.53,77 29,77.6 29.5, 75.15 29.53)’), ←↩

4326);

--result--POLYGON((75.15 29.53,77 29,77.6 29.5,75.15 29.53))--a 3d polygonSELECT ST_AsEWKT(ST_Polygon(ST_GeomFromEWKT(’LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, ←↩

75.15 29.53 1)’), 4326));

result------SRID=4326;POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

See Also

ST_AsEWKT, ST_AsText, ST_GeomFromEWKT, ST_GeomFromText, ST_LineMerge, ST_MakePolygon

8.3.34 ST_PolygonFromText

ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1.

Synopsis

geometry ST_PolygonFromText(text WKT);geometry ST_PolygonFromText(text WKT, integer srid);

Description

Makes a Geometry from WKT with the given SRID. If SRID is not give, it defaults to -1. Returns null if WKT is not a polygon.


NoteIf you are absolutely sure all your WKT geometries are polygons, don’t use this function. It is slower thanST_GeomFromText since it adds an additional validation step.






Examples

SELECT ST_PolygonFromText(’POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 ←↩42.3903701743239,

-71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 ←↩42.3902909739571))’);

st_polygonfromtext------------------010300000001000000050000006...

SELECT ST_PolygonFromText(’POINT(1 2)’) IS NULL as point_is_notpoly;

point_is_not_poly----------t

See Also

ST_GeomFromText

8.3.35 ST_WKBToSQL

ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an aliasname for ST_GeomFromWKB that takes no srid

Synopsis

geometry ST_WKBToSQL(bytea WKB);

Description


See Also

ST_GeomFromWKB

8.3.36 ST_WKTToSQL

ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias namefor ST_GeomFromText

Synopsis

geometry ST_WKTToSQL(text WKT);

Description



See Also

ST_GeomFromText

8.4 Geometry Accessors

8.4.1 GeometryType

GeometryType — Returns the type of the geometry as a string. Eg: ’LINESTRING’, ’POLYGON’, ’MULTIPOINT’, etc.

Synopsis

text GeometryType(geometry geomA);

Description

Returns the type of the geometry as a string. Eg: ’LINESTRING’, ’POLYGON’, ’MULTIPOINT’, etc.

OGC SPEC s2.1.1.1 - Returns the name of the instantiable subtype of Geometry of which this Geometry instance is a member.The name of the instantiable subtype of Geometry is returned as a string.

NoteThis function also indicates if the geometry is measured, by returning a string of the form ’POINTM’.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.






Examples

SELECT GeometryType(ST_GeomFromText(’LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 ←↩29.07)’));

geometrytype--------------LINESTRING

SELECT ST_GeometryType(ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 ←↩0 0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’));

--resultPOLYHEDRALSURFACE



SELECT GeometryType(geom) as resultFROM(SELECT

ST_GeomFromEWKT(’TIN (((0 0 0,0 0 1,0 1 0,0 0 0

)), ((0 0 0,0 1 0,1 1 0,0 0 0

)))’) AS geom

) AS g;result

--------TIN

See Also

ST_GeometryType

8.4.2 ST_Boundary

ST_Boundary — Returns the closure of the combinatorial boundary of this Geometry.

Synopsis

geometry ST_Boundary(geometry geomA);

Description

Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described insection 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resultingboundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.

Performed by the GEOS module

NotePrior to 2.0.0, this function throws an exception if used with GEOMETRYCOLLECTION. From 2.0.0 up it will returnNULL instead (unsupported input).

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. OGC SPEC s2.1.1.1





Examples

SELECT ST_AsText(ST_Boundary(ST_GeomFromText(’LINESTRING(1 1,0 0, -1 1)’)));st_astext-----------MULTIPOINT(1 1,-1 1)

SELECT ST_AsText(ST_Boundary(ST_GeomFromText(’POLYGON((1 1,0 0, -1 1, 1 1))’)));st_astext----------LINESTRING(1 1,0 0,-1 1,1 1)

--Using a 3d polygonSELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT(’POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))’)));

st_asewkt-----------------------------------LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)

--Using a 3d multilinestringSELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT(’MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 ←↩

0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )’)));

st_asewkt----------MULTIPOINT(-1 1 1,1 1 0.75)

See Also

ST_ExteriorRing, ST_MakePolygon

8.4.3 ST_CoordDim

ST_CoordDim — Return the coordinate dimension of the ST_Geometry value.

Synopsis

integer ST_CoordDim(geometry geomA);

Description

Return the coordinate dimension of the ST_Geometry value.

This is the MM compliant alias name for ST_NDims









Examples

SELECT ST_CoordDim(’CIRCULARSTRING(1 2 3, 1 3 4, 5 6 7, 8 9 10, 11 12 13)’);---result--

3

SELECT ST_CoordDim(ST_Point(1,2));--result--

2

See Also

ST_NDims

8.4.4 ST_Dimension

ST_Dimension — The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension.

Synopsis

integer ST_Dimension(geometry g);

Description

The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension. OGC SPECs2.1.1.1 - returns 0 for POINT, 1 for LINESTRING, 2 for POLYGON, and the largest dimension of the components of a GEOM-ETRYCOLLECTION. If unknown (empty geometry) null is returned.


Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given emptygeometry.

NotePrior to 2.0.0, this function throws an exception if used with empty geometry.



Examples

SELECT ST_Dimension(’GEOMETRYCOLLECTION(LINESTRING(1 1,0 0),POINT(0 0))’);ST_Dimension-----------1


See Also

ST_NDims

8.4.5 ST_EndPoint

ST_EndPoint — Returns the last point of a LINESTRING geometry as a POINT.

Synopsis

boolean ST_EndPoint(geometry g);

Description

Returns the last point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING.



NoteChanged: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single linemultilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any othermultilinestring. The older behavior was an undocumented feature, but people who assumed they had their data storedas LINESTRING may experience these returning NULL in 2.0 now.

Examples

postgis=# SELECT ST_AsText(ST_EndPoint(’LINESTRING(1 1, 2 2, 3 3)’::geometry));st_astext

------------POINT(3 3)

(1 row)

postgis=# SELECT ST_EndPoint(’POINT(1 1)’::geometry) IS NULL AS is_null;is_null

----------t

(1 row)

--3d endpointSELECT ST_AsEWKT(ST_EndPoint(’LINESTRING(1 1 2, 1 2 3, 0 0 5)’));

st_asewkt--------------POINT(0 0 5)

(1 row)

See Also

ST_PointN, ST_StartPoint


8.4.6 ST_Envelope

ST_Envelope — Returns a geometry representing the double precision (float8) bounding box of the supplied geometry.

Synopsis

geometry ST_Envelope(geometry g1);

Description

Returns the float8 minimum bounding box for the supplied geometry, as a geometry. The polygon is defined by the cornerpoints of the bounding box ((MINX, MINY), (MINX, MAXY), (MAXX, MAXY), (MAXX, MINY), (MINX, MINY)). (PostGIS will adda ZMIN/ZMAX coordinate as well).

Degenerate cases (vertical lines, points) will return a geometry of lower dimension than POLYGON, ie. POINT or LINESTRING.

Availability: 1.5.0 behavior changed to output double precision instead of float4



Examples

SELECT ST_AsText(ST_Envelope(’POINT(1 3)’::geometry));st_astext

------------POINT(1 3)

(1 row)

SELECT ST_AsText(ST_Envelope(’LINESTRING(0 0, 1 3)’::geometry));st_astext

--------------------------------POLYGON((0 0,0 3,1 3,1 0,0 0))

(1 row)

SELECT ST_AsText(ST_Envelope(’POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))’::geometry ←↩));

st_astext--------------------------------------------------------------POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))

(1 row)SELECT ST_AsText(ST_Envelope(’POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))’:: ←↩

geometry));st_astext

--------------------------------------------------------------POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))

(1 row)

SELECT Box3D(geom), Box2D(geom), ST_AsText(ST_Envelope(geom)) As envelopewktFROM (SELECT ’POLYGON((0 0, 0 1000012333334.34545678, 1.0000001 1, 1.0000001 0, 0 0))’:: ←↩

geometry As geom) As foo;



See Also

Box2D, Box3D

8.4.7 ST_ExteriorRing

ST_ExteriorRing — Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometryis not a polygon. Will not work with MULTIPOLYGON

Synopsis

geometry ST_ExteriorRing(geometry a_polygon);

Description

Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon.

NoteOnly works with POLYGON geometry types


This method implements the SQL/MM specification. SQL-MM 3: 8.2.3, 8.3.3


Examples

--If you have a table of polygonsSELECT gid, ST_ExteriorRing(the_geom) AS eringFROM sometable;

--If you have a table of MULTIPOLYGONs--and want to return a MULTILINESTRING composed of the exterior rings of each polygonSELECT gid, ST_Collect(ST_ExteriorRing(the_geom)) AS erings

FROM (SELECT gid, (ST_Dump(the_geom)).geom As the_geomFROM sometable) As foo

GROUP BY gid;

--3d ExampleSELECT ST_AsEWKT(

ST_ExteriorRing(ST_GeomFromEWKT(’POLYGON((0 0 1, 1 1 1, 1 2 1, 1 1 1, 0 0 1))’))

);

st_asewkt---------LINESTRING(0 0 1,1 1 1,1 2 1,1 1 1,0 0 1)



See Also

ST_InteriorRingN, ST_Boundary, ST_NumInteriorRings

8.4.8 ST_GeometryN

ST_GeometryN — Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING,MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL.

Synopsis

geometry ST_GeometryN(geometry geomA, integer n);

Description

Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING,MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL

NoteIndex is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead.

NoteIf you want to extract all geometries, of a geometry, ST_Dump is more efficient and will also work for singular geoms.


Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry forST_GeometryN(..,1) case.









Standard Examples

--Extracting a subset of points from a 3d multipointSELECT n, ST_AsEWKT(ST_GeometryN(the_geom, n)) As geomewktFROM (VALUES (ST_GeomFromEWKT(’MULTIPOINT(1 2 7, 3 4 7, 5 6 7, 8 9 10)’) ),( ST_GeomFromEWKT(’MULTICURVE(CIRCULARSTRING(2.5 2.5,4.5 2.5, 3.5 3.5), (10 11, 12 11))’) )

)As foo(the_geom)CROSS JOIN generate_series(1,100) n

WHERE n <= ST_NumGeometries(the_geom);

n | geomewkt---+-----------------------------------------1 | POINT(1 2 7)2 | POINT(3 4 7)3 | POINT(5 6 7)4 | POINT(8 9 10)1 | CIRCULARSTRING(2.5 2.5,4.5 2.5,3.5 3.5)2 | LINESTRING(10 11,12 11)

--Extracting all geometries (useful when you want to assign an id)SELECT gid, n, ST_GeometryN(the_geom, n)FROM sometable CROSS JOIN generate_series(1,100) nWHERE n <= ST_NumGeometries(the_geom);

Polyhedral Surfaces, TIN and Triangle Examples

-- Polyhedral surface example-- Break a Polyhedral surface into its facesSELECT ST_AsEWKT(ST_GeometryN(p_geom,3)) As geom_ewkt

FROM (SELECT ST_GeomFromEWKT(’POLYHEDRALSURFACE(((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)))’) AS p_geom ) AS a;

geom_ewkt------------------------------------------POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))

-- TIN --SELECT ST_AsEWKT(ST_GeometryN(geom,2)) as wkt

FROM(SELECT


)), ((0 0 0,0 1 0,1 1 0,0 0 0

))


)’) AS geom) AS g;

-- result --wkt

-------------------------------------TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

See Also

ST_Dump, ST_NumGeometries

8.4.9 ST_GeometryType

ST_GeometryType — Return the geometry type of the ST_Geometry value.

Synopsis

text ST_GeometryType(geometry g1);

Description

Returns the type of the geometry as a string. EG: ’ST_Linestring’, ’ST_Polygon’,’ST_MultiPolygon’ etc. This function differsfrom GeometryType(geometry) in the case of the string and ST in front that is returned, as well as the fact that it will not indicatewhether the geometry is measured.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.




Examples

SELECT ST_GeometryType(ST_GeomFromText(’LINESTRING(77.29 29.07,77.42 29.26,77.27 ←↩29.31,77.29 29.07)’));

--resultST_LineString


--resultST_PolyhedralSurface


--resultST_PolyhedralSurface


SELECT ST_GeometryType(geom) as resultFROM(SELECT


)), ((0 0 0,0 1 0,1 1 0,0 0 0

)))’) AS geom

) AS g;result

--------ST_Tin

See Also

GeometryType

8.4.10 ST_InteriorRingN

ST_InteriorRingN — Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not apolygon or the given N is out of range.

Synopsis

geometry ST_InteriorRingN(geometry a_polygon, integer n);

Description

Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N isout of range. index starts at 1.

NoteThis will not work for MULTIPOLYGONs. Use in conjunction with ST_Dump for MULTIPOLYGONS






Examples

SELECT ST_AsText(ST_InteriorRingN(the_geom, 1)) As the_geomFROM (SELECT ST_BuildArea(

ST_Collect(ST_Buffer(ST_Point(1,2), 20,3),ST_Buffer(ST_Point(1, 2), 10,3))) As the_geom

) as foo

See Also

ST_ExteriorRing ST_BuildArea, ST_Collect, ST_Dump, ST_NumInteriorRing, ST_NumInteriorRings

8.4.11 ST_IsClosed

ST_IsClosed — Returns TRUE if the LINESTRING’s start and end points are coincident. For Polyhedral surface is closed(volumetric).

Synopsis

boolean ST_IsClosed(geometry g);

Description

Returns TRUE if the LINESTRING’s start and end points are coincident. For Polyhedral Surfaces, it tells you if the surface isareal (open) or volumetric (closed).



NoteSQL-MM defines the result of ST_IsClosed(NULL) to be 0, while PostGIS returns NULL.





Line String and Point Examples

postgis=# SELECT ST_IsClosed(’LINESTRING(0 0, 1 1)’::geometry);st_isclosed

-------------f

(1 row)



postgis=# SELECT ST_IsClosed(’LINESTRING(0 0, 0 1, 1 1, 0 0)’::geometry);st_isclosed

-------------t

(1 row)

postgis=# SELECT ST_IsClosed(’MULTILINESTRING((0 0, 0 1, 1 1, 0 0),(0 0, 1 1))’::geometry);st_isclosed

-------------f

(1 row)

postgis=# SELECT ST_IsClosed(’POINT(0 0)’::geometry);st_isclosed

-------------t

(1 row)

postgis=# SELECT ST_IsClosed(’MULTIPOINT((0 0), (1 1))’::geometry);st_isclosed

-------------t

(1 row)

Polyhedral Surface Examples

-- A cube --SELECT ST_IsClosed(ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 ←↩

0 0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’));

st_isclosed-------------t

-- Same as cube but missing a side --SELECT ST_IsClosed(ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 ←↩

0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)) )’));

st_isclosed-------------f

See Also

ST_IsRing

8.4.12 ST_IsCollection

ST_IsCollection — Returns TRUE if the argument is a collection (MULTI*, GEOMETRYCOLLECTION, ...)


Synopsis

boolean ST_IsCollection(geometry g);

Description

Returns TRUE if the geometry type of the argument is either:

• GEOMETRYCOLLECTION

• MULTI{POINT,POLYGON,LINESTRING,CURVE,SURFACE}

• COMPOUNDCURVE

NoteThis function analyzes the type of the geometry. This means that it will return TRUE on collections that are empty orthat contain a single element.



Examples

postgis=# SELECT ST_IsCollection(’LINESTRING(0 0, 1 1)’::geometry);st_iscollection

-------------f

(1 row)

postgis=# SELECT ST_IsCollection(’MULTIPOINT EMPTY’::geometry);st_iscollection

-------------t

(1 row)

postgis=# SELECT ST_IsCollection(’MULTIPOINT((0 0))’::geometry);st_iscollection

-------------t

(1 row)

postgis=# SELECT ST_IsCollection(’MULTIPOINT((0 0), (42 42))’::geometry);st_iscollection

-------------t

(1 row)

postgis=# SELECT ST_IsCollection(’GEOMETRYCOLLECTION(POINT(0 0))’::geometry);st_iscollection

-------------t

(1 row)


See Also

ST_NumGeometries

8.4.13 ST_IsEmpty

ST_IsEmpty — Returns true if this Geometry is an empty geometrycollection, polygon, point etc.

Synopsis

boolean ST_IsEmpty(geometry geomA);

Description

Returns true if this Geometry is an empty geometry. If true, then this Geometry represents an empty geometry collection,polygon, point etc.

NoteSQL-MM defines the result of ST_IsEmpty(NULL) to be 0, while PostGIS returns NULL.




WarningChanged: 2.0.0 In prior versions of PostGIS ST_GeomFromText(’GEOMETRYCOLLECTION(EMPTY)’) was allowed.This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards

Examples

SELECT ST_IsEmpty(ST_GeomFromText(’GEOMETRYCOLLECTION EMPTY’));st_isempty

------------t

(1 row)

SELECT ST_IsEmpty(ST_GeomFromText(’POLYGON EMPTY’));st_isempty

------------t

(1 row)

SELECT ST_IsEmpty(ST_GeomFromText(’POLYGON((1 2, 3 4, 5 6, 1 2))’));

st_isempty------------



f(1 row)

SELECT ST_IsEmpty(ST_GeomFromText(’POLYGON((1 2, 3 4, 5 6, 1 2))’)) = false;?column?

----------t

(1 row)

SELECT ST_IsEmpty(ST_GeomFromText(’CIRCULARSTRING EMPTY’));st_isempty

------------t

(1 row)

8.4.14 ST_IsRing

ST_IsRing — Returns TRUE if this LINESTRING is both closed and simple.

Synopsis

boolean ST_IsRing(geometry g);

Description

Returns TRUE if this LINESTRING is both ST_IsClosed (ST_StartPoint((g)) ~= ST_Endpoint((g))) and ST_IsSimple(does not self intersect).



NoteSQL-MM defines the result of ST_IsRing(NULL) to be 0, while PostGIS returns NULL.

Examples

SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)FROM (SELECT ’LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)’::geometry AS the_geom) AS foo;st_isring | st_isclosed | st_issimple

-----------+-------------+-------------t | t | t

(1 row)

SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)FROM (SELECT ’LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)’::geometry AS the_geom) AS foo;st_isring | st_isclosed | st_issimple

-----------+-------------+-------------f | t | f

(1 row)



See Also

ST_IsClosed, ST_IsSimple, ST_StartPoint, ST_EndPoint

8.4.15 ST_IsSimple

ST_IsSimple — Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency.

Synopsis

boolean ST_IsSimple(geometry geomA);

Description

Returns true if this Geometry has no anomalous geometric points, such as self intersection or self tangency. For more informationon the OGC’s definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"

NoteSQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL.




Examples

SELECT ST_IsSimple(ST_GeomFromText(’POLYGON((1 2, 3 4, 5 6, 1 2))’));st_issimple

-------------t

(1 row)

SELECT ST_IsSimple(ST_GeomFromText(’LINESTRING(1 1,2 2,2 3.5,1 3,1 2,2 1)’));st_issimple

-------------f

(1 row)

See Also

ST_IsValid

8.4.16 ST_IsValid

ST_IsValid — Returns true if the ST_Geometry is well formed.



Synopsis

boolean ST_IsValid(geometry g);boolean ST_IsValid(geometry g, integer flags);

Description

Test if an ST_Geometry value is well formed. For geometries that are invalid, the PostgreSQL NOTICE will provide detailsof why it is not valid. For more information on the OGC’s definition of geometry simplicity and validity, refer to "EnsuringOpenGIS compliancy of geometries"

NoteSQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL.

The version accepting flags is available starting with 2.0.0 and requires GEOS >= 3.3.0. Such version does not print a NOTICEexplaining the invalidity. Allowed flags are documented in ST_IsValidDetail.



Examples

SELECT ST_IsValid(ST_GeomFromText(’LINESTRING(0 0, 1 1)’)) As good_line,ST_IsValid(ST_GeomFromText(’POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))’)) As bad_poly

--resultsNOTICE: Self-intersection at or near point 0 0good_line | bad_poly

-----------+----------t | f

See Also

ST_IsSimple, ST_IsValidReason, ST_IsValidDetail, ST_Summary

8.4.17 ST_IsValidReason

ST_IsValidReason — Returns text stating if a geometry is valid or not and if not valid, a reason why.

Synopsis

text ST_IsValidReason(geometry geomA);text ST_IsValidReason(geometry geomA, integer flags);

Description

Returns text stating if a geometry is valid or not an if not valid, a reason why.

Useful in combination with ST_IsValid to generate a detailed report of invalid geometries and reasons.

Allowed flags are documented in ST_IsValidDetail.

Availability: 1.4 - requires GEOS >= 3.1.0.

Availability: 2.0 - requires GEOS >= 3.3.0 for the version taking flags.



Examples

--First 3 Rejects from a successful quintuplet experimentSELECT gid, ST_IsValidReason(the_geom) as validity_infoFROM(SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gidFROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid

FROM generate_series(-4,6) x1CROSS JOIN generate_series(2,5) y1CROSS JOIN generate_series(1,8) z1WHERE x1 > y1*0.5 AND z1 < x1*y1) As eINNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1 ←↩

*1, z1*2) As lineFROM generate_series(-3,6) x1CROSS JOIN generate_series(2,5) y1CROSS JOIN generate_series(1,10) z1WHERE x1 > y1*0.75 AND z1 < x1*y1) As f

ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))GROUP BY gid, e.buff) As quintuplet_experimentWHERE ST_IsValid(the_geom) = falseORDER BY gidLIMIT 3;

gid | validity_info------+--------------------------5330 | Self-intersection [32 5]5340 | Self-intersection [42 5]5350 | Self-intersection [52 5]

--simple exampleSELECT ST_IsValidReason(’LINESTRING(220227 150406,2220227 150407,222020 150410)’);

st_isvalidreason------------------Valid Geometry

See Also

ST_IsValid, ST_Summary

8.4.18 ST_IsValidDetail

ST_IsValidDetail — Returns a valid_detail (valid,reason,location) row stating if a geometry is valid or not and if not valid, areason why and a location where.

Synopsis

valid_detail ST_IsValidDetail(geometry geom);valid_detail ST_IsValidDetail(geometry geom, integer flags);

Description

Returns a valid_detail row, formed by a boolean (valid) stating if a geometry is valid, a varchar (reason) stating a reason why itis invalid and a geometry (location) pointing out where it is invalid.


Useful to substitute and improve the combination of ST_IsValid and ST_IsValidReason to generate a detailed report of invalidgeometries.

The ’flags’ argument is a bitfield. It can have the following values:

• 1: Consider self-intersecting rings forming holes as valid. This is also know as "the ESRI flag". Note that this is against theOGC model.


Examples

--First 3 Rejects from a successful quintuplet experimentSELECT gid, reason(ST_IsValidDetail(the_geom)), ST_AsText(location(ST_IsValidDetail( ←↩

the_geom))) as locationFROM(SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gidFROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid

FROM generate_series(-4,6) x1CROSS JOIN generate_series(2,5) y1CROSS JOIN generate_series(1,8) z1WHERE x1 > y1*0.5 AND z1 < x1*y1) As eINNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1 ←↩

*1, z1*2) As lineFROM generate_series(-3,6) x1CROSS JOIN generate_series(2,5) y1CROSS JOIN generate_series(1,10) z1WHERE x1 > y1*0.75 AND z1 < x1*y1) As f

ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))GROUP BY gid, e.buff) As quintuplet_experimentWHERE ST_IsValid(the_geom) = falseORDER BY gidLIMIT 3;

gid | reason | location------+-------------------+-------------5330 | Self-intersection | POINT(32 5)5340 | Self-intersection | POINT(42 5)5350 | Self-intersection | POINT(52 5)

--simple exampleSELECT * FROM ST_IsValidDetail(’LINESTRING(220227 150406,2220227 150407,222020 150410)’);

valid | reason | location-------+--------+----------t | |

See Also

ST_IsValid, ST_IsValidReason

8.4.19 ST_M

ST_M — Return the M coordinate of the point, or NULL if not available. Input must be a point.


Synopsis

float ST_M(geometry a_point);

Description

Return the M coordinate of the point, or NULL if not available. Input must be a point.

NoteThis is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list.




Examples

SELECT ST_M(ST_GeomFromEWKT(’POINT(1 2 3 4)’));st_m

------4

(1 row)

See Also

ST_GeomFromEWKT, ST_X, ST_Y, ST_Z

8.4.20 ST_NDims

ST_NDims — Returns coordinate dimension of the geometry as a small int. Values are: 2,3 or 4.

Synopsis

integer ST_NDims(geometry g1);

Description

Returns the coordinate dimension of the geometry. PostGIS supports 2 - (x,y) , 3 - (x,y,z) or 2D with measure - x,y,m, and 4 - 3Dwith measure space x,y,z,m




Examples

SELECT ST_NDims(ST_GeomFromText(’POINT(1 1)’)) As d2point,ST_NDims(ST_GeomFromEWKT(’POINT(1 1 2)’)) As d3point,ST_NDims(ST_GeomFromEWKT(’POINTM(1 1 0.5)’)) As d2pointm;

d2point | d3point | d2pointm---------+---------+----------

2 | 3 | 3

See Also

ST_CoordDim, ST_Dimension, ST_GeomFromEWKT

8.4.21 ST_NPoints

ST_NPoints — Return the number of points (vertexes) in a geometry.

Synopsis

integer ST_NPoints(geometry g1);

Description

Return the number of points in a geometry. Works for all geometries.


NotePrior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+




Examples

SELECT ST_NPoints(ST_GeomFromText(’LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 ←↩29.07)’));

--result4

--Polygon in 3D spaceSELECT ST_NPoints(ST_GeomFromEWKT(’LINESTRING(77.29 29.07 1,77.42 29.26 0,77.27 29.31 ←↩

-1,77.29 29.07 3)’))--result4


See Also

ST_NumPoints

8.4.22 ST_NRings

ST_NRings — If the geometry is a polygon or multi-polygon returns the number of rings.

Synopsis

integer ST_NRings(geometry geomA);

Description

If the geometry is a polygon or multi-polygon returns the number of rings. Unlike NumInteriorRings, it counts the outer rings aswell.



Examples

SELECT ST_NRings(the_geom) As Nrings, ST_NumInteriorRings(the_geom) As ninterringsFROM (SELECT ST_GeomFromText(’POLYGON((1 2, 3 4, 5 6, 1 2))’) As the_geom) As foo ←↩

;nrings | ninterrings

--------+-------------1 | 0

(1 row)

See Also

ST_NumInteriorRings

8.4.23 ST_NumGeometries

ST_NumGeometries — If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for singlegeometries will return 1, otherwise return NULL.

Synopsis

integer ST_NumGeometries(geometry geom);


Description

Returns the number of Geometries. If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries,for single geometries will return 1, otherwise return NULL.


Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns1 for single geometries e.g POLYGON, LINESTRING, POINT.





Examples

--Prior versions would have returned NULL for this -- in 2.0.0 this returns 1SELECT ST_NumGeometries(ST_GeomFromText(’LINESTRING(77.29 29.07,77.42 29.26,77.27 ←↩

29.31,77.29 29.07)’));--result1

--Geometry Collection Example - multis count as one geom in a collectionSELECT ST_NumGeometries(ST_GeomFromEWKT(’GEOMETRYCOLLECTION(MULTIPOINT(-2 3 , -2 2),LINESTRING(5 5 ,10 10),POLYGON((-7 4.2,-7.1 5,-7.1 4.3,-7 4.2)))’));--result3

See Also

ST_GeometryN, ST_Multi

8.4.24 ST_NumInteriorRings

ST_NumInteriorRings — Return the number of interior rings of the first polygon in the geometry. This will work with bothPOLYGON and MULTIPOLYGON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry.

Synopsis

integer ST_NumInteriorRings(geometry a_polygon);

Description

Return the number of interior rings of the first polygon in the geometry. This will work with both POLYGON and MULTIPOLY-GON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry.



Examples

--If you have a regular polygonSELECT gid, field1, field2, ST_NumInteriorRings(the_geom) AS numholesFROM sometable;

--If you have multipolygons--And you want to know the total number of interior rings in the MULTIPOLYGONSELECT gid, field1, field2, SUM(ST_NumInteriorRings(the_geom)) AS numholesFROM (SELECT gid, field1, field2, (ST_Dump(the_geom)).geom As the_geom

FROM sometable) As fooGROUP BY gid, field1,field2;

See Also

ST_NumInteriorRing

8.4.25 ST_NumInteriorRing

ST_NumInteriorRing — Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings.

Synopsis

integer ST_NumInteriorRing(geometry a_polygon);

Description

Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings. The OpenGIS specsare ambiguous about the exact function naming, so we provide both spellings.


See Also

ST_NumInteriorRings

8.4.26 ST_NumPatches

ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.

Synopsis

integer ST_NumPatches(geometry g1);


Description

Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This is an alias forST_NumGeometries to support MM naming. Faster to use ST_NumGeometries if you don’t care about MM convention.

Availability: 2.0.0



This method implements the SQL/MM specification. SQL-MM 3: ?


Examples

SELECT ST_NumPatches(ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 ←↩0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’));--result6

See Also

ST_GeomFromEWKT, ST_NumGeometries

8.4.27 ST_NumPoints

ST_NumPoints — Return the number of points in an ST_LineString or ST_CircularString value.

Synopsis

integer ST_NumPoints(geometry g1);

Description

Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with Linestrings as thespecs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertexes for not just line strings. Considerusing ST_NPoints instead which is multi-purpose and works with many geometry types.






Examples

SELECT ST_NumPoints(ST_GeomFromText(’LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 ←↩29.07)’));--result4

See Also

ST_NPoints

8.4.28 ST_PatchN

ST_PatchN — Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSUR-FACEM. Otherwise, return NULL.

Synopsis

geometry ST_PatchN(geometry geomA, integer n);

Description

>Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Other-wise, return NULL. This returns the same answer as ST_GeometryN for Polyhedral Surfaces. Using ST_GemoetryN is faster.

NoteIndex is 1-based.

NoteIf you want to extract all geometries, of a geometry, ST_Dump is more efficient.

Availability: 2.0.0




Examples


--Extract the 2nd face of the polyhedral surfaceSELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewktFROM (VALUES (ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),

((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’)) ) As ←↩

foo(geom);

geomewkt---+-----------------------------------------POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

See Also

ST_AsEWKT, ST_GeomFromEWKT, ST_Dump, ST_GeometryN, ST_NumGeometries

8.4.29 ST_PointN

ST_PointN — Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is nolinestring in the geometry.

Synopsis

geometry ST_PointN(geometry a_linestring, integer n);

Description

Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in thegeometry.

NoteIndex is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead.

NoteIf you want to get the nth point of each line string in a multilinestring, use in conjunction with ST_Dump







Examples

-- Extract all POINTs from a LINESTRINGSELECT ST_AsText(

ST_PointN(column1,generate_series(1, ST_NPoints(column1))))

FROM ( VALUES (’LINESTRING(0 0, 1 1, 2 2)’::geometry) ) AS foo;

st_astext------------POINT(0 0)POINT(1 1)POINT(2 2)

(3 rows)

--Example circular stringSELECT ST_AsText(ST_PointN(ST_GeomFromText(’CIRCULARSTRING(1 2, 3 2, 1 2)’),2));

st_astext----------POINT(3 2)

See Also

ST_NPoints

8.4.30 ST_SRID

ST_SRID — Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.

Synopsis

integer ST_SRID(geometry g1);

Description

Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. Section 4.3.1

Notespatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transforma-tions from one spatial reference system to another. So verifying you have the right spatial reference system identifier isimportant if you plan to ever transform your geometries.






Examples

SELECT ST_SRID(ST_GeomFromText(’POINT(-71.1043 42.315)’,4326));--result4326

See Also

Section 4.3.1, ST_GeomFromText, ST_SetSRID, ST_Transform

8.4.31 ST_StartPoint

ST_StartPoint — Returns the first point of a LINESTRING geometry as a POINT.

Synopsis

geometry ST_StartPoint(geometry geomA);

Description

Returns the first point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING.



NoteChanged: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single linemultilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any othermultilinestring. The older behavior was an undocumented feature, but people who assumed they had their data storedas LINESTRING may experience these returning NULL in 2.0 now.

Examples

SELECT ST_AsText(ST_StartPoint(’LINESTRING(0 1, 0 2)’::geometry));st_astext

------------POINT(0 1)

(1 row)

SELECT ST_StartPoint(’POINT(0 1)’::geometry) IS NULL AS is_null;is_null

----------t

(1 row)

--3d lineSELECT ST_AsEWKT(ST_StartPoint(’LINESTRING(0 1 1, 0 2 2)’::geometry));st_asewkt

------------POINT(0 1 1)

(1 row)


See Also

ST_EndPoint, ST_PointN

8.4.32 ST_Summary

ST_Summary — Returns a text summary of the contents of the geometry.

Synopsis

text ST_Summary(geometry g);text ST_Summary(geography g);

Description

Returns a text summary of the contents of the geometry.

Flags shown square brackets after the geometry type have the following meaning:

• M: has M ordinate

• Z: has Z ordinate

• B: has a cached bounding box

• G: is geodetic (geography)

Availability: 1.2.2 - 2.0.0 added support for geography

Examples

=# SELECT ST_Summary(ST_GeomFromText(’LINESTRING(0 0, 1 1)’)) as geom,ST_Summary(ST_GeogFromText(’POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))’)) geog;

geom | geog-----------------------------+--------------------------LineString[B] with 2 points | Polygon[BG] with 1 rings

: ring 0 has 5 points:

(1 row)

=# SELECT ST_Summary(ST_GeogFromText(’LINESTRING(0 0 1, 1 1 1)’)) As geog_line,ST_Summary(ST_GeomFromText(’POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))’)) As ←↩

geom_poly;;

geog_line | geom_poly-------------------------------+--------------------------LineString[ZBG] with 2 points | Polygon[ZB] with 1 rings

: ring 0 has 5 points:

(1 row)

See Also

PostGIS_DropBBox, PostGIS_AddBBox, ST_Force_3DM, ST_Force_3DZ, ST_Force_2D, geography

ST_IsValid, ST_IsValid, ST_IsValidReason, ST_IsValidDetail


8.4.33 ST_X

ST_X — Return the X coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_X(geometry a_point);

Description

Return the X coordinate of the point, or NULL if not available. Input must be a point.

NoteIf you want to get the max min x values of any geometry look at ST_XMin, ST_XMax functions.



Examples

SELECT ST_X(ST_GeomFromEWKT(’POINT(1 2 3 4)’));st_x

------1

(1 row)

SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT(’LINESTRING(1 2 3 4, 1 1 1 1)’)));st_y

------1.5

(1 row)

See Also

ST_Centroid, ST_GeomFromEWKT, ST_M, ST_XMax, ST_XMin, ST_Y, ST_Z

8.4.34 ST_XMax

ST_XMax — Returns X maxima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_XMax(box3d aGeomorBox2DorBox3D);


Description

Returns X maxima of a bounding box 2d or 3d or a geometry.

NoteAlthough this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behaviordefined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that willnot auto-cast.



Examples

SELECT ST_XMax(’BOX3D(1 2 3, 4 5 6)’);st_xmax-------4

SELECT ST_XMax(ST_GeomFromText(’LINESTRING(1 3 4, 5 6 7)’));st_xmax-------5

SELECT ST_XMax(CAST(’BOX(-3 2, 3 4)’ As box2d));st_xmax-------3--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a ←↩

BOX3DSELECT ST_XMax(’LINESTRING(1 3, 5 6)’);

--ERROR: BOX3D parser - doesnt start with BOX3D(

SELECT ST_XMax(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 ←↩150406 3)’));

st_xmax--------220288.248780547

See Also

ST_XMin, ST_YMax, ST_YMin, ST_ZMax, ST_ZMin

8.4.35 ST_XMin

ST_XMin — Returns X minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_XMin(box3d aGeomorBox2DorBox3D);


Description

Returns X minima of a bounding box 2d or 3d or a geometry.




Examples

SELECT ST_XMin(’BOX3D(1 2 3, 4 5 6)’);st_xmin-------1

SELECT ST_XMin(ST_GeomFromText(’LINESTRING(1 3 4, 5 6 7)’));st_xmin-------1

SELECT ST_XMin(CAST(’BOX(-3 2, 3 4)’ As box2d));st_xmin--------3--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a ←↩

BOX3DSELECT ST_XMin(’LINESTRING(1 3, 5 6)’);


SELECT ST_XMin(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 ←↩150406 3)’));

st_xmin--------220186.995121892

See Also

ST_XMax, ST_YMax, ST_YMin, ST_ZMax, ST_ZMin

8.4.36 ST_Y

ST_Y — Return the Y coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_Y(geometry a_point);


Description

Return the Y coordinate of the point, or NULL if not available. Input must be a point.




Examples

SELECT ST_Y(ST_GeomFromEWKT(’POINT(1 2 3 4)’));st_y

------2

(1 row)

SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT(’LINESTRING(1 2 3 4, 1 1 1 1)’)));st_y

------1.5

(1 row)

See Also

ST_Centroid, ST_GeomFromEWKT, ST_M, ST_X, ST_YMax, ST_YMin, ST_Z

8.4.37 ST_YMax

ST_YMax — Returns Y maxima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_YMax(box3d aGeomorBox2DorBox3D);

Description

Returns Y maxima of a bounding box 2d or 3d or a geometry.






Examples

SELECT ST_YMax(’BOX3D(1 2 3, 4 5 6)’);st_ymax-------5

SELECT ST_YMax(ST_GeomFromText(’LINESTRING(1 3 4, 5 6 7)’));st_ymax-------6

SELECT ST_YMax(CAST(’BOX(-3 2, 3 4)’ As box2d));st_ymax-------4--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a ←↩

BOX3DSELECT ST_YMax(’LINESTRING(1 3, 5 6)’);


SELECT ST_YMax(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 ←↩150406 3)’));

st_ymax--------150506.126829327

See Also

ST_XMin, ST_XMax, ST_YMin, ST_ZMax, ST_ZMin

8.4.38 ST_YMin

ST_YMin — Returns Y minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_YMin(box3d aGeomorBox2DorBox3D);

Description

Returns Y minima of a bounding box 2d or 3d or a geometry.





Examples

SELECT ST_YMin(’BOX3D(1 2 3, 4 5 6)’);st_ymin-------2

SELECT ST_YMin(ST_GeomFromText(’LINESTRING(1 3 4, 5 6 7)’));st_ymin-------3

SELECT ST_YMin(CAST(’BOX(-3 2, 3 4)’ As box2d));st_ymin-------2--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a ←↩

BOX3DSELECT ST_YMin(’LINESTRING(1 3, 5 6)’);


SELECT ST_YMin(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 ←↩150406 3)’));

st_ymin--------150406

See Also

ST_GeomFromEWKT, ST_XMin, ST_XMax, ST_YMax, ST_ZMax, ST_ZMin

8.4.39 ST_Z

ST_Z — Return the Z coordinate of the point, or NULL if not available. Input must be a point.

Synopsis

float ST_Z(geometry a_point);

Description

Return the Z coordinate of the point, or NULL if not available. Input must be a point.



Examples

SELECT ST_Z(ST_GeomFromEWKT(’POINT(1 2 3 4)’));st_z

------3


(1 row)

See Also

ST_GeomFromEWKT, ST_M, ST_X, ST_Y, ST_ZMax, ST_ZMin

8.4.40 ST_ZMax

ST_ZMax — Returns Z minima of a bounding box 2d or 3d or a geometry.

Synopsis

float ST_ZMax(box3d aGeomorBox2DorBox3D);

Description

Returns Z maxima of a bounding box 2d or 3d or a geometry.




Examples

SELECT ST_ZMax(’BOX3D(1 2 3, 4 5 6)’);st_zmax-------6

SELECT ST_ZMax(ST_GeomFromEWKT(’LINESTRING(1 3 4, 5 6 7)’));st_zmax-------7

SELECT ST_ZMax(’BOX3D(-3 2 1, 3 4 1)’ );st_zmax-------1--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a ←↩

BOX3DSELECT ST_ZMax(’LINESTRING(1 3 4, 5 6 7)’);


SELECT ST_ZMax(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 ←↩150406 3)’));


st_zmax--------3

See Also

ST_GeomFromEWKT, ST_XMin, ST_XMax, ST_YMax, ST_YMin, ST_ZMax

8.4.41 ST_Zmflag

ST_Zmflag — Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.

Synopsis

smallint ST_Zmflag(geometry geomA);

Description

Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.



Examples

SELECT ST_Zmflag(ST_GeomFromEWKT(’LINESTRING(1 2, 3 4)’));st_zmflag

-----------0

SELECT ST_Zmflag(ST_GeomFromEWKT(’LINESTRINGM(1 2 3, 3 4 3)’));st_zmflag

-----------1

SELECT ST_Zmflag(ST_GeomFromEWKT(’CIRCULARSTRING(1 2 3, 3 4 3, 5 6 3)’));st_zmflag

-----------2

SELECT ST_Zmflag(ST_GeomFromEWKT(’POINT(1 2 3 4)’));st_zmflag

-----------3

See Also

ST_CoordDim, ST_NDims, ST_Dimension

8.4.42 ST_ZMin

ST_ZMin — Returns Z minima of a bounding box 2d or 3d or a geometry.


Synopsis

float ST_ZMin(box3d aGeomorBox2DorBox3D);

Description

Returns Z minima of a bounding box 2d or 3d or a geometry.




Examples

SELECT ST_ZMin(’BOX3D(1 2 3, 4 5 6)’);st_zmin-------3

SELECT ST_ZMin(ST_GeomFromEWKT(’LINESTRING(1 3 4, 5 6 7)’));st_zmin-------4

SELECT ST_ZMin(’BOX3D(-3 2 1, 3 4 1)’ );st_zmin-------1--Observe THIS DOES NOT WORK because it will try to autocast the string representation to a ←↩

BOX3DSELECT ST_ZMin(’LINESTRING(1 3 4, 5 6 7)’);


SELECT ST_ZMin(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 ←↩150406 3)’));

st_zmin--------1

See Also

ST_GeomFromEWKT, ST_GeomFromText, ST_XMin, ST_XMax, ST_YMax, ST_YMin, ST_ZMax

8.5 Geometry Editors

8.5.1 ST_AddPoint

ST_AddPoint — Adds a point to a LineString before point <position> (0-based index).


Synopsis

geometry ST_AddPoint(geometry linestring, geometry point);

geometry ST_AddPoint(geometry linestring, geometry point, integer position);

Description

Adds a point to a LineString before point <position> (0-based index). Third parameter can be omitted or set to -1 for appending.

Availability: 1.1.0


Examples

--guarantee all linestrings in a table are closed--by adding the start point of each linestring to the end of the line string--only for those that are not closedUPDATE sometableSET the_geom = ST_AddPoint(the_geom, ST_StartPoint(the_geom))FROM sometableWHERE ST_IsClosed(the_geom) = false;

--Adding point to a 3-d lineSELECT ST_AsEWKT(ST_AddPoint(ST_GeomFromEWKT(’LINESTRING(0 0 1, 1 1 1)’), ST_MakePoint ←↩

(1, 2, 3)));

--resultst_asewkt----------LINESTRING(0 0 1,1 1 1,1 2 3)

See Also

ST_RemovePoint, ST_SetPoint

8.5.2 ST_Affine

ST_Affine — Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.

Synopsis

geometry ST_Affine(geometry geomA, float a, float b, float c, float d, float e, float f, float g, float h, float i, float xoff, float yoff,float zoff);geometry ST_Affine(geometry geomA, float a, float b, float d, float e, float xoff, float yoff);

Description

Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step.

Version 1: The call

ST_Affine(geom, a, b, c, d, e, f, g, h, i, xoff, yoff, zoff)


represents the transformation matrix

/ a b c xoff \| d e f yoff || g h i zoff |\ 0 0 0 1 /

and the vertices are transformed as follows:

x’ = a*x + b*y + c*z + xoffy’ = d*x + e*y + f*z + yoffz’ = g*x + h*y + i*z + zoff

All of the translate / scale functions below are expressed via such an affine transformation.

Version 2: Applies a 2d affine transformation to the geometry. The call

ST_Affine(geom, a, b, d, e, xoff, yoff)

represents the transformation matrix

/ a b 0 xoff \ / a b xoff \| d e 0 yoff | rsp. | d e yoff || 0 0 1 0 | \ 0 0 1 /\ 0 0 0 1 /

and the vertices are transformed as follows:

x’ = a*x + b*y + xoffy’ = d*x + e*y + yoffz’ = z

This method is a subcase of the 3D method above.


Availability: 1.1.2. Name changed from Affine to ST_Affine in 1.2.2






Examples


--Rotate a 3d line 180 degrees about the z axis. Note this is long-hand for doing ←↩ST_Rotate();

SELECT ST_AsEWKT(ST_Affine(the_geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, ←↩0, 0, 1, 0, 0, 0)) As using_affine,

ST_AsEWKT(ST_Rotate(the_geom, pi())) As using_rotateFROM (SELECT ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 4 3)’) As the_geom) As foo;

using_affine | using_rotate-----------------------------+-----------------------------LINESTRING(-1 -2 3,-1 -4 3) | LINESTRING(-1 -2 3,-1 -4 3)

(1 row)

--Rotate a 3d line 180 degrees in both the x and z axisSELECT ST_AsEWKT(ST_Affine(the_geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin( ←↩

pi()), 0, sin(pi()), cos(pi()), 0, 0, 0))FROM (SELECT ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 4 3)’) As the_geom) As foo;

st_asewkt-------------------------------LINESTRING(-1 -2 -3,-1 -4 -3)

(1 row)

See Also

ST_Rotate, ST_Scale, ST_Translate, ST_TransScale

8.5.3 ST_Force_2D

ST_Force_2D — Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X andY coordinates.

Synopsis

geometry ST_Force_2D(geometry geomA);

Description

Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates.This is useful for force OGC-compliant output (since OGC only specifies 2-D geometries).





Examples

SELECT ST_AsEWKT(ST_Force_2D(ST_GeomFromEWKT(’CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 ←↩6 2)’)));st_asewkt

-------------------------------------CIRCULARSTRING(1 1,2 3,4 5,6 7,5 6)


SELECT ST_AsEWKT(ST_Force_2D(’POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2)) ←↩’));

st_asewkt----------------------------------------------POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))

See Also

ST_Force_3D

8.5.4 ST_Force_3D

ST_Force_3D — Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ.

Synopsis


Description

Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ. If a geometry has no Z component, then a 0 Zcoordinate is tacked on.





Examples

--Nothing happens to an already 3D geometrySELECT ST_AsEWKT(ST_Force_3D(ST_GeomFromEWKT(’CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 ←↩

2, 5 6 2)’)));st_asewkt

-----------------------------------------------CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

SELECT ST_AsEWKT(ST_Force_3D(’POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))’));

st_asewkt--------------------------------------------------------------POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3DZ


8.5.5 ST_Force_3DZ

ST_Force_3DZ — Forces the geometries into XYZ mode. This is a synonym for ST_Force_3D.

Synopsis

geometry ST_Force_3DZ(geometry geomA);

Description

Forces the geometries into XYZ mode. This is a synonym for ST_Force_3DZ. If a geometry has no Z component, then a 0 Zcoordinate is tacked on.





Examples

--Nothing happens to an already 3D geometrySELECT ST_AsEWKT(ST_Force_3DZ(ST_GeomFromEWKT(’CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 ←↩

6 2)’)));st_asewkt

-----------------------------------------------CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

SELECT ST_AsEWKT(ST_Force_3DZ(’POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))’));

st_asewkt--------------------------------------------------------------POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D

8.5.6 ST_Force_3DM

ST_Force_3DM — Forces the geometries into XYM mode.

Synopsis

geometry ST_Force_3DM(geometry geomA);


Description

Forces the geometries into XYM mode. If a geometry has no M component, then a 0 M coordinate is tacked on. If it has a Zcomponent, then Z is removed


Examples

--Nothing happens to an already 3D geometrySELECT ST_AsEWKT(ST_Force_3DM(ST_GeomFromEWKT(’CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 ←↩


------------------------------------------------CIRCULARSTRINGM(1 1 0,2 3 0,4 5 0,6 7 0,5 6 0)

SELECT ST_AsEWKT(ST_Force_3DM(’POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1) ←↩)’));

st_asewkt---------------------------------------------------------------POLYGONM((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D, ST_GeomFromEWKT

8.5.7 ST_Force_4D

ST_Force_4D — Forces the geometries into XYZM mode.

Synopsis


Description

Forces the geometries into XYZM mode. 0 is tacked on for missing Z and M dimensions.



Examples

--Nothing happens to an already 3D geometrySELECT ST_AsEWKT(ST_Force_4D(ST_GeomFromEWKT(’CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 ←↩


---------------------------------------------------------


CIRCULARSTRING(1 1 2 0,2 3 2 0,4 5 2 0,6 7 2 0,5 6 2 0)

SELECT ST_AsEWKT(ST_Force_4D(’MULTILINESTRINGM((0 0 1,0 5 2,5 0 3,0 0 4),(1 1 1,3 1 1,1 3 ←↩1,1 1 1))’));

st_asewkt--------------------------------------------------------------------------------------MULTILINESTRING((0 0 0 1,0 5 0 2,5 0 0 3,0 0 0 4),(1 1 0 1,3 1 0 1,1 3 0 1,1 1 0 1))

See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D

8.5.8 ST_Force_Collection

ST_Force_Collection — Converts the geometry into a GEOMETRYCOLLECTION.

Synopsis

geometry ST_Force_Collection(geometry geomA);

Description

Converts the geometry into a GEOMETRYCOLLECTION. This is useful for simplifying the WKB representation.


Availability: 1.2.2, prior to 1.3.4 this function will crash with Curves. This is fixed in 1.3.4+




Examples

SELECT ST_AsEWKT(ST_Force_Collection(’POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 ←↩1,1 1 1))’));

st_asewkt----------------------------------------------------------------------------------GEOMETRYCOLLECTION(POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1)))

SELECT ST_AsText(ST_Force_Collection(’CIRCULARSTRING(220227 150406,2220227 150407,220227 ←↩150406)’));

st_astext--------------------------------------------------------------------------------GEOMETRYCOLLECTION(CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))

(1 row)


-- POLYHEDRAL example --SELECT ST_AsEWKT(ST_Force_Collection(’POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))’))

st_asewkt----------------------------------------------------------------------------------GEOMETRYCOLLECTION(

POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))

)

See Also

ST_AsEWKT, ST_Force_2D, ST_Force_3DM, ST_Force_3D, ST_GeomFromEWKT

8.5.9 ST_ForceRHR

ST_ForceRHR — Forces the orientation of the vertices in a polygon to follow the Right-Hand-Rule.

Synopsis

boolean ST_ForceRHR(geometry g);

Description

Forces the orientation of the vertices in a polygon to follow the Right-Hand-Rule. In GIS terminology, this means that the areathat is bounded by the polygon is to the right of the boundary. In particular, the exterior ring is orientated in a clockwise directionand the interior rings in a counter-clockwise direction.




Examples

SELECT ST_AsEWKT(ST_ForceRHR(’POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))’)

);st_asewkt

--------------------------------------------------------------POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))

(1 row)


See Also

ST_BuildArea, ST_Polygonize, ST_Reverse

8.5.10 ST_LineMerge

ST_LineMerge — Returns a (set of) LineString(s) formed by sewing together a MULTILINESTRING.

Synopsis

geometry ST_LineMerge(geometry amultilinestring);

Description

Returns a (set of) LineString(s) formed by sewing together the constituent line work of a MULTILINESTRING.

NoteOnly use with MULTILINESTRING/LINESTRINGs. If you feed a polygon or geometry collection into this function, it willreturn an empty GEOMETRYCOLLECTION

Availability: 1.1.0

Noterequires GEOS >= 2.1.0

Examples

SELECT ST_AsText(ST_LineMerge(ST_GeomFromText(’MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))’)

));st_astext-------------------------------------------------------------------------------------------------- ←↩

LINESTRING(-29 -27,-30 -29.7,-36 -31,-45 -33,-46 -32)(1 row)

--If can’t be merged - original MULTILINESTRING is returnedSELECT ST_AsText(ST_LineMerge(ST_GeomFromText(’MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45.2 -33.2,-46 -32)) ←↩

’)));st_astext----------------MULTILINESTRING((-45.2 -33.2,-46 -32),(-29 -27,-30 -29.7,-36 -31,-45 -33))

See Also

ST_Segmentize, ST_Line_Substring


8.5.11 ST_CollectionExtract

ST_CollectionExtract — Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type.

Synopsis

geometry ST_CollectionExtract(geometry collection, integer type);

Description

Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type. Sub-geometries that arenot the specified type are ignored. If there are no sub-geometries of the right type, an EMPTY geometry will be returned. Onlypoints, lines and polygons are supported. Type numbers are 1 == POINT, 2 == LINESTRING, 3 == POLYGON.

Availability: 1.5.0

NotePrior to 1.5.3 this function returned non-collection inputs untouched, no matter type. In 1.5.3 non-matching singlegeometries result in a NULL return. In of 2.0.0 every case of missing match results in a typed EMPTY return.

Examples

-- Constants: 1 == POINT, 2 == LINESTRING, 3 == POLYGONSELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText(’GEOMETRYCOLLECTION( ←↩

GEOMETRYCOLLECTION(POINT(0 0)))’),1));st_astext---------------MULTIPOINT(0 0)(1 row)

SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText(’GEOMETRYCOLLECTION( ←↩GEOMETRYCOLLECTION(LINESTRING(0 0, 1 1)),LINESTRING(2 2, 3 3))’),2));

st_astext---------------MULTILINESTRING((0 0, 1 1), (2 2, 3 3))(1 row)

See Also

ST_Multi, ST_Dump, ST_CollectionHomogenize

8.5.12 ST_CollectionHomogenize

ST_CollectionHomogenize — Given a geometry collection, returns the "simplest" representation of the contents.

Synopsis

geometry ST_CollectionHomogenize(geometry collection);


Description

Given a geometry collection, returns the "simplest" representation of the contents. Singletons will be returned as singletons.Collections that are homogeneous will be returned as the appropriate multi-type.

Availability: 2.0.0

Examples

SELECT ST_AsText(ST_CollectionHomogenize(’GEOMETRYCOLLECTION(POINT(0 0))’));


(1 row)

SELECT ST_AsText(ST_CollectionHomogenize(’GEOMETRYCOLLECTION(POINT(0 0),POINT(1 1))’));

st_astext---------------------MULTIPOINT(0 0,1 1)

(1 row)

See Also

ST_Multi, ST_CollectionExtract

8.5.13 ST_Multi

ST_Multi — Returns the geometry as a MULTI* geometry. If the geometry is already a MULTI*, it is returned unchanged.

Synopsis

geometry ST_Multi(geometry g1);

Description

Returns the geometry as a MULTI* geometry. If the geometry is already a MULTI*, it is returned unchanged.

Examples

SELECT ST_AsText(ST_Multi(ST_GeomFromText(’POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))’)));st_astext-------------------------------------------------------------------------------------------------- ←↩

MULTIPOLYGON(((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416)))(1 row)

See Also

ST_AsText


8.5.14 ST_RemovePoint

ST_RemovePoint — Removes point from a linestring. Offset is 0-based.

Synopsis

geometry ST_RemovePoint(geometry linestring, integer offset);

Description

Removes point from a linestring. Useful for turning a closed ring into an open line string

Availability: 1.1.0


Examples

--guarantee no LINESTRINGS are closed--by removing the end point. The below assumes the_geom is of type LINESTRINGUPDATE sometable

SET the_geom = ST_RemovePoint(the_geom, ST_NPoints(the_geom) - 1)FROM sometableWHERE ST_IsClosed(the_geom) = true;

See Also

ST_AddPoint, ST_NPoints, ST_NumPoints

8.5.15 ST_Reverse

ST_Reverse — Returns the geometry with vertex order reversed.

Synopsis

geometry ST_Reverse(geometry g1);

Description

Can be used on any geometry and reverses the order of the vertexes.

Examples

SELECT ST_AsText(the_geom) as line, ST_AsText(ST_Reverse(the_geom)) As reverselineFROM(SELECT ST_MakeLine(ST_MakePoint(1,2),

ST_MakePoint(1,10)) As the_geom) as foo;--result

line | reverseline---------------------+----------------------LINESTRING(1 2,1 10) | LINESTRING(1 10,1 2)


8.5.16 ST_Rotate

ST_Rotate — Rotate a geometry rotRadians counter-clockwise about an origin.

Synopsis

geometry ST_Rotate(geometry geomA, float rotRadians);geometry ST_Rotate(geometry geomA, float rotRadians, float x0, float y0);geometry ST_Rotate(geometry geomA, float rotRadians, geometry pointOrigin);

Description

Rotates geometry rotRadians counter-clockwise about the origin. The rotation origin can be specified either as a POINT geome-try, or as x and y coordinates. If the origin is not specified, the geometry is rotated about POINT(0 0).


Enhanced: 2.0.0 additional parameters for specifying the origin of rotation were added.

Availability: 1.1.2. Name changed from Rotate to ST_Rotate in 1.2.2





Examples

--Rotate 180 degreesSELECT ST_AsEWKT(ST_Rotate(’LINESTRING (50 160, 50 50, 100 50)’, pi()));

st_asewkt---------------------------------------LINESTRING(-50 -160,-50 -50,-100 -50)

(1 row)

--Rotate 30 degrees counter-clockwise at x=50, y=160SELECT ST_AsEWKT(ST_Rotate(’LINESTRING (50 160, 50 50, 100 50)’, pi()/6, 50, 160));

st_asewkt---------------------------------------------------------------------------LINESTRING(50 160,105 64.7372055837117,148.301270189222 89.7372055837117)

(1 row)

--Rotate 60 degrees clockwise from centroidSELECT ST_AsEWKT(ST_Rotate(geom, -pi()/3, ST_Centroid(geom)))FROM (SELECT ’LINESTRING (50 160, 50 50, 100 50)’::geometry AS geom) AS foo;

st_asewkt--------------------------------------------------------------LINESTRING(116.4225 130.6721,21.1597 75.6721,46.1597 32.3708)

(1 row)

See Also

ST_Affine, ST_RotateX, ST_RotateY, ST_RotateZ


8.5.17 ST_RotateX

ST_RotateX — Rotate a geometry rotRadians about the X axis.

Synopsis

geometry ST_RotateX(geometry geomA, float rotRadians);

Description

Rotate a geometry geomA - rotRadians about the X axis.

NoteST_RotateX(geomA, rotRadians) is short-hand for ST_Affine(geomA, 1, 0, 0, 0, cos(rot-Radians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0).


Availability: 1.1.2. Name changed from RotateX to ST_RotateX in 1.2.2




Examples

--Rotate a line 90 degrees along x-axisSELECT ST_AsEWKT(ST_RotateX(ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 1 1)’), pi()/2));

st_asewkt---------------------------LINESTRING(1 -3 2,1 -1 1)

See Also

ST_Affine, ST_RotateY, ST_RotateZ

8.5.18 ST_RotateY

ST_RotateY — Rotate a geometry rotRadians about the Y axis.

Synopsis

geometry ST_RotateY(geometry geomA, float rotRadians);


Description

Rotate a geometry geomA - rotRadians about the y axis.

NoteST_RotateY(geomA, rotRadians) is short-hand for ST_Affine(geomA, cos(rotRadians), 0,sin(rotRadians), 0, 1, 0, -sin(rotRadians), 0, cos(rotRadians), 0, 0, 0).

Availability: 1.1.2. Name changed from RotateY to ST_RotateY in 1.2.2





Examples

--Rotate a line 90 degrees along y-axisSELECT ST_AsEWKT(ST_RotateY(ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 1 1)’), pi()/2));

st_asewkt---------------------------LINESTRING(3 2 -1,1 1 -1)

See Also

ST_Affine, ST_RotateX, ST_RotateZ

8.5.19 ST_RotateZ

ST_RotateZ — Rotate a geometry rotRadians about the Z axis.

Synopsis

geometry ST_RotateZ(geometry geomA, float rotRadians);

Description

Rotate a geometry geomA - rotRadians about the Z axis.

NoteThis is a synonym for ST_Rotate


NoteST_RotateZ(geomA, rotRadians) is short-hand for SELECT ST_Affine(geomA, cos(rotRadia-ns), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0, 1, 0, 0,0).


Availability: 1.1.2. Name changed from RotateZ to ST_RotateZ in 1.2.2






Examples

--Rotate a line 90 degrees along z-axisSELECT ST_AsEWKT(ST_RotateZ(ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 1 1)’), pi()/2));

st_asewkt---------------------------LINESTRING(-2 1 3,-1 1 1)

--Rotate a curved circle around z-axisSELECT ST_AsEWKT(ST_RotateZ(the_geom, pi()/2))FROM (SELECT ST_LineToCurve(ST_Buffer(ST_GeomFromText(’POINT(234 567)’), 3)) As the_geom) ←↩

As foo;

st_asewkt---------------------------------------------------------------------------------------------------------------------------- ←↩

CURVEPOLYGON(CIRCULARSTRING(-567 237,-564.87867965644 236.12132034356,-564 ←↩234,-569.12132034356 231.87867965644,-567 237))

See Also

ST_Affine, ST_RotateX, ST_RotateY

8.5.20 ST_Scale

ST_Scale — Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor,Yfactor, Zfactor).


Synopsis

geometry ST_Scale(geometry geomA, float XFactor, float YFactor, float ZFactor);geometry ST_Scale(geometry geomA, float XFactor, float YFactor);

Description

Scales the geometry to a new size by multiplying the ordinates with the parameters. Ie: ST_Scale(geom, Xfactor, Yfactor,Zfactor).

NoteST_Scale(geomA, XFactor, YFactor, ZFactor) is short-hand for ST_Affine(geomA, XFacto-r, 0, 0, 0, YFactor, 0, 0, 0, ZFactor, 0, 0, 0).


Availability: 1.1.0.






Examples

--Version 1: scale X, Y, ZSELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 1 1)’), 0.5, 0.75, 0.8));

st_asewkt--------------------------------------LINESTRING(0.5 1.5 2.4,0.5 0.75 0.8)

--Version 2: Scale X YSELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 1 1)’), 0.5, 0.75));

st_asewkt----------------------------------LINESTRING(0.5 1.5 3,0.5 0.75 1)

See Also

ST_Affine, ST_TransScale


8.5.21 ST_Segmentize

ST_Segmentize — Return a modified geometry having no segment longer than the given distance. Distance computation isperformed in 2d only.

Synopsis

geometry ST_Segmentize(geometry geomA, float max_length);

Description

Returns a modified geometry having no segment longer than the given distance. Distance computation is performed in 2d only.

Availability: 1.2.2

NoteThis will only increase segments. It will not lengthen segments shorter than max length

Examples

SELECT ST_AsText(ST_Segmentize(ST_GeomFromText(’MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))’)

,5));st_astext-------------------------------------------------------------------------------------------------- ←↩

MULTILINESTRING((-29 -27,-30 -29.7,-34.886615700134 -30.758766735029,-36 -31,-40.8809353009198 -32.0846522890933,-45 -33),(-45 -33,-46 -32))(1 row)

SELECT ST_AsText(ST_Segmentize(ST_GeomFromText(’POLYGON((-29 28, -30 40, -29 28))’),10));st_astext-----------------------POLYGON((-29 28,-29.8304547985374 37.9654575824488,-30 40,-29.1695452014626 ←↩

30.0345424175512,-29 28))(1 row)

See Also

ST_Line_Substring

8.5.22 ST_SetPoint

ST_SetPoint — Replace point N of linestring with given point. Index is 0-based.

Synopsis

geometry ST_SetPoint(geometry linestring, integer zerobasedposition, geometry point);


Description

Replace point N of linestring with given point. Index is 0-based. This is especially useful in triggers when trying to maintainrelationship of joints when one vertex moves.

Availability: 1.1.0


Examples

--Change first point in line string from -1 3 to -1 1SELECT ST_AsText(ST_SetPoint(’LINESTRING(-1 2,-1 3)’, 0, ’POINT(-1 1)’));

st_astext-----------------------LINESTRING(-1 1,-1 3)

---Change last point in a line string (lets play with 3d linestring this time)SELECT ST_AsEWKT(ST_SetPoint(foo.the_geom, ST_NumPoints(foo.the_geom) - 1, ST_GeomFromEWKT ←↩

(’POINT(-1 1 3)’)))FROM (SELECT ST_GeomFromEWKT(’LINESTRING(-1 2 3,-1 3 4, 5 6 7)’) As the_geom) As foo;

st_asewkt-----------------------LINESTRING(-1 2 3,-1 3 4,-1 1 3)

See Also

ST_AddPoint, ST_NPoints, ST_NumPoints, ST_PointN, ST_RemovePoint

8.5.23 ST_SetSRID

ST_SetSRID — Sets the SRID on a geometry to a particular integer value.

Synopsis

geometry ST_SetSRID(geometry geom, integer srid);

Description

Sets the SRID on a geometry to a particular integer value. Useful in constructing bounding boxes for queries.

NoteThis function does not transform the geometry coordinates in any way - it simply sets the meta data defining the spatialreference system the geometry is assumed to be in. Use ST_Transform if you want to transform the geometry into anew projection.





Examples

-- Mark a point as WGS 84 long lat --

SELECT ST_SetSRID(ST_Point(-123.365556, 48.428611),4326) As wgs84long_lat;-- the ewkt representation (wrap with ST_AsEWKT) -SRID=4326;POINT(-123.365556 48.428611)

-- Mark a point as WGS 84 long lat and then transform to web mercator (Spherical Mercator) --

SELECT ST_Transform(ST_SetSRID(ST_Point(-123.365556, 48.428611),4326),3785) As spere_merc;-- the ewkt representation (wrap with ST_AsEWKT) -SRID=3785;POINT(-13732990.8753491 6178458.96425423)

See Also

Section 4.3.1, ST_AsEWKT, ST_Point, ST_SRID, ST_Transform, UpdateGeometrySRID

8.5.24 ST_SnapToGrid

ST_SnapToGrid — Snap all points of the input geometry to a regular grid.

Synopsis

geometry ST_SnapToGrid(geometry geomA, float originX, float originY, float sizeX, float sizeY);geometry ST_SnapToGrid(geometry geomA, float sizeX, float sizeY);geometry ST_SnapToGrid(geometry geomA, float size);geometry ST_SnapToGrid(geometry geomA, geometry pointOrigin, float sizeX, float sizeY, float sizeZ, float sizeM);

Description

Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive pointsfalling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type.Collapsed geometries in a collection are stripped from it. Useful for reducing precision.

Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, mustbe a point) and cell sizes. Specify 0 as size for any dimension you don’t want to snap to a grid.

NoteThe returned geometry might loose its simplicity (see ST_IsSimple).

NoteBefore release 1.1.0 this function always returned a 2d geometry. Starting at 1.1.0 the returned geometry will have samedimensionality as the input one with higher dimension values untouched. Use the version taking a second geometryargument to define all grid dimensions.

Availability: 1.0.0RC1

Availability: 1.1.0 - Z and M support



Examples

--Snap your geometries to a precision grid of 10^-3UPDATE mytable

SET the_geom = ST_SnapToGrid(the_geom, 0.001);

SELECT ST_AsText(ST_SnapToGrid(ST_GeomFromText(’LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667) ←↩

’),0.001)

);st_astext

-------------------------------------LINESTRING(1.112 2.123,4.111 3.237)--Snap a 4d geometry

SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT(’LINESTRING(-1.1115678 2.123 2.3456 1.11111,4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)’),

ST_GeomFromEWKT(’POINT(1.12 2.22 3.2 4.4444)’),0.1, 0.1, 0.1, 0.01) );

st_asewkt------------------------------------------------------------------------------LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)

--With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m ←↩and z the same

SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT(’LINESTRING(-1.1115678 2.123 3 2.3456,4.111111 3.2374897 3.1234 1.1111)’),0.01) );

st_asewkt---------------------------------------------------------LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)

See Also

ST_Snap, ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_GeomFromEWKT, ST_Simplify

8.5.25 ST_Snap

ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.

Synopsis

geometry ST_Snap(geometry input, geometry reference, float tolerance);

Description

Snaps the vertices and segments of a geometry another Geometry’s vertices. A snap distance tolerance is used to control wheresnapping is performed.

Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (whichcause problems during noding and intersection calculation).

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided usingheuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.


NoteThe returned geometry might loose its simplicity (see ST_IsSimple) and validity (see ST_IsValid).

Availability: 2.0.0 requires GEOS >= 3.3.0.

Examples

A multipolygon shown with a linestring (before any snapping)


A multipolygon snapped to linestring to tolerance: 1.01 ofdistance. The new multipolygon is shown with reference

linestring

SELECT ST_AsText(ST_Snap(poly,line, ←↩ST_Distance(poly,line)*1.01)) AS polysnapped

FROM (SELECTST_GeomFromText(’MULTIPOLYGON(

((26 125, 26 200, 126 200, 126 125, ←↩26 125 ),( 51 150, 101 150, 76 175, 51 150 ) ←↩

),(( 151 100, 151 200, 176 175, 151 ←↩

100 )))’) As poly,ST_GeomFromText(’LINESTRING (5 ←↩

107, 54 84, 101 100)’) As line

) As foo;

polysnapped--------------------------------------------------------------------- ←↩

MULTIPOLYGON(((26 125,26 200,126 200,126 ←↩125,101 100,26 125),

(51 150,101 150,76 175,51 150)),((151 ←↩100,151 200,176 175,151 100)))

A multipolygon snapped to linestring to tolerance: 1.25 ofdistance. The new multipolygon is shown with reference

linestring

SELECT ST_AsText(ST_Snap(poly,line, ST_Distance(poly, ←↩line)*1.25)

) AS polysnappedFROM (SELECT

ST_GeomFromText(’MULTIPOLYGON((( 26 125, 26 200, 126 200, 126 125, ←↩26 125 ),( 51 150, 101 150, 76 175, 51 150 ) ←↩

),(( 151 100, 151 200, 176 175, 151 ←↩


107, 54 84, 101 100)’) As line

) As foo;

polysnapped--------------------------------------------------------------------- ←↩

MULTIPOLYGON(((5 107,26 200,126 200,126 ←↩125,101 100,54 84,5 107),

(51 150,101 150,76 175,51 150)),((151 ←↩100,151 200,176 175,151 100)))


The linestring snapped to the original multipolygon attolerance 1.01 of distance. The new linestring is shown

with reference multipolygon

SELECT ST_AsText(ST_Snap(line, poly, ST_Distance(poly, ←↩line)*1.01)

) AS linesnappedFROM (SELECT

ST_GeomFromText(’MULTIPOLYGON(((26 125, 26 200, 126 200, 126 125, ←↩26 125),(51 150, 101 150, 76 175, 51 150 )) ←↩

,((151 100, 151 200, 176 175, 151 ←↩

100)))’) As poly,ST_GeomFromText(’LINESTRING (5 ←↩

107, 54 84, 101 100)’) As line) As foo;

linesnapped----------------------------------------LINESTRING(5 107,26 125,54 84,101 100)

The linestring snapped to the original multipolygon attolerance 1.25 of distance. The new linestring is shown

with reference multipolygon

SELECT ST_AsText(ST_Snap(line, poly, ST_Distance(poly, ←↩

line)*1.25)) AS linesnapped

FROM (SELECTST_GeomFromText(’MULTIPOLYGON(

(( 26 125, 26 200, 126 200, 126 125, ←↩26 125 ),(51 150, 101 150, 76 175, 51 150 )) ←↩

,((151 100, 151 200, 176 175, 151 ←↩


107, 54 84, 101 100)’) As line) As foo;

linesnapped---------------------------------------LINESTRING(26 125,54 84,101 100)

See Also

ST_SnapToGrid

8.5.26 ST_Transform

ST_Transform — Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter.

Synopsis

geometry ST_Transform(geometry g1, integer srid);


Description

Returns a new geometry with its coordinates transformed to spatial reference system referenced by the SRID integer parameter.The destination SRID must exist in the SPATIAL_REF_SYS table.

ST_Transform is often confused with ST_SetSRID(). ST_Transform actually changes the coordinates of a geometry from onespatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the geometry

NoteRequires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiledin.

NoteIf using more than one transformation, it is useful to have a functional index on the commonly used transformations totake advantage of index usage.






Examples

Change Mass state plane US feet geometry to WGS 84 long lat

SELECT ST_AsText(ST_Transform(ST_GeomFromText(’POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))’,2249),4326)) As wgs_geom;

wgs_geom---------------------------POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,

-71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.1776848522251 42.3902896512902));(1 row)

--3D Circular String exampleSELECT ST_AsEWKT(ST_Transform(ST_GeomFromEWKT(’SRID=2249;CIRCULARSTRING(743238 2967416 ←↩

1,743238 2967450 2,743265 2967450 3,743265.625 2967416 3,743238 2967416 4)’),4326));

st_asewkt--------------------------------------------------------------------------------------SRID=4326;CIRCULARSTRING(-71.1776848522251 42.3902896512902 1,-71.1776843766326 ←↩

42.3903829478009 2,-71.1775844305465 42.3903826677917 3,-71.1775825927231 42.3902893647987 3,-71.1776848522251 42.3902896512902 4)


Example of creating a partial functional index. For tables where you are not sure all the geometries will be filled in, its best to usea partial index that leaves out null geometries which will both conserve space and make your index smaller and more efficient.

CREATE INDEX idx_the_geom_26986_parcelsON parcelsUSING gist(ST_Transform(the_geom, 26986))WHERE the_geom IS NOT NULL;

Configuring transformation behaviour

Sometimes coordinate transformation involving a grid-shift can fail, for example if PROJ.4 has not been built with grid-shift filesor the coordinate does not lie within the range for which the grid shift is defined. By default, PostGIS will throw an error if agrid shift file is not present, but this behaviour can be configured on a per-SRID basis by altering the proj4text value within thespatial_ref_sys table.

For example, the proj4text parameter +datum=NAD87 is a shorthand form for the following +nadgrids parameter:

+nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat

The @ prefix means no error is reported if the files are not present, but if the end of the list is reached with no file having beenappropriate (ie. found and overlapping) then an error is issued.

If, conversely, you wanted to ensure that at least the standard files were present, but that if all files were scanned without a hit anull transformation is applied you could use:

+nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null

The null grid shift file is a valid grid shift file covering the whole world and applying no shift. So for a complete example, if youwanted to alter PostGIS so that transformations to SRID 4267 that didn’t lie within the correct range did not throw an ERROR,you would use the following:

UPDATE spatial_ref_sys SET proj4text = ’+proj=longlat +ellps=clrk66 +nadgrids=@conus, ←↩@alaska,@ntv2_0.gsb,@ntv1_can.dat,null +no_defs’ WHERE srid = 4267;

See Also

PostGIS_Full_Version, ST_AsText, ST_SetSRID, UpdateGeometrySRID

8.5.27 ST_Translate

ST_Translate — Translates the geometry to a new location using the numeric parameters as offsets. Ie: ST_Translate(geom, X,Y) or ST_Translate(geom, X, Y,Z).

Synopsis

geometry ST_Translate(geometry g1, float deltax, float deltay);geometry ST_Translate(geometry g1, float deltax, float deltay, float deltaz);

Description

Returns a new geometry whose coordinates are translated delta x,delta y,delta z units. Units are based on the units defined inspatial reference (SRID) for this geometry.



Availability: 1.2.2



Examples

Move a point 1 degree longitude

SELECT ST_AsText(ST_Translate(ST_GeomFromText(’POINT(-71.01 42.37)’,4326),1,0)) As ←↩wgs_transgeomtxt;

wgs_transgeomtxt---------------------POINT(-70.01 42.37)

Move a linestring 1 degree longitude and 1/2 degree latitude

SELECT ST_AsText(ST_Translate(ST_GeomFromText(’LINESTRING(-71.01 42.37,-71.11 42.38)’,4326) ←↩,1,0.5)) As wgs_transgeomtxt;

wgs_transgeomtxt---------------------------------------LINESTRING(-70.01 42.87,-70.11 42.88)

Move a 3d point

SELECT ST_AsEWKT(ST_Translate(CAST(’POINT(0 0 0)’ As geometry), 5, 12,3));st_asewkt---------POINT(5 12 3)

Move a curve and a point

SELECT ST_AsText(ST_Translate(ST_Collect(’CURVEPOLYGON(CIRCULARSTRING(4 3,3.12 0.878,1 ←↩0,-1.121 5.1213,6 7, 8 9,4 3))’,’POINT(1 3)’),1,2));

st_astext------------------------------------------------------------------------------------------------------------ ←↩

GEOMETRYCOLLECTION(CURVEPOLYGON(CIRCULARSTRING(5 5,4.12 2.878,2 2,-0.121 7.1213,7 9,9 11,5 ←↩5)),POINT(2 5))

See Also

ST_Affine, ST_AsText, ST_GeomFromText

8.5.28 ST_TransScale

ST_TransScale — Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args,working in 2D only.


Synopsis

geometry ST_TransScale(geometry geomA, float deltaX, float deltaY, float XFactor, float YFactor);

Description

Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.

NoteST_TransScale(geomA, deltaX, deltaY, XFactor, YFactor) is short-hand for ST_Affine(g-eomA, XFactor, 0, 0, 0, YFactor, 0, 0, 0, 1, deltaX*XFactor, deltaY*YFactor,0).


Availability: 1.1.0.



Examples

SELECT ST_AsEWKT(ST_TransScale(ST_GeomFromEWKT(’LINESTRING(1 2 3, 1 1 1)’), 0.5, 1, 1, 2));st_asewkt

-----------------------------LINESTRING(1.5 6 3,1.5 4 1)

--Buffer a point to get an approximation of a circle, convert to curve and then translate ←↩1,2 and scale it 3,4

SELECT ST_AsText(ST_Transscale(ST_LineToCurve(ST_Buffer(’POINT(234 567)’, 3)),1,2,3,4));st_astext

------------------------------------------------------------------------------------------------------------------------------ ←↩

CURVEPOLYGON(CIRCULARSTRING(714 2276,711.363961030679 2267.51471862576,705 ←↩2264,698.636038969321 2284.48528137424,714 2276))

See Also

ST_Affine, ST_Translate

8.6 Geometry Outputs

8.6.1 ST_AsBinary

ST_AsBinary — Return the Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.


Synopsis

bytea ST_AsBinary(geometry g1);bytea ST_AsBinary(geometry g1, text NDR_or_XDR);bytea ST_AsBinary(geography g1);bytea ST_AsBinary(geography g1, text NDR_or_XDR);

Description

Returns the Well-Known Binary representation of the geometry. There are 2 variants of the function. The first variant takes noendian encoding parameter and defaults to server machine endian. The second variant takes a second argument denoting theencoding - using little-endian (’NDR’) or big-endian (’XDR’) encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

NoteThe WKB spec does not include the SRID. To get the WKB with SRID format use ST_AsEWKB

NoteST_AsBinary is the reverse of ST_GeomFromWKB for geometry. Use ST_GeomFromWKB to convert to a postgisgeometry from ST_AsBinary representation.

NoteThe default behavior in PostgreSQL 9.0 has been changed to output bytea in hex encoding. ST_AsBinary is the reverseof ST_GeomFromWKB for geometry. If your GUI tools require the old behavior, then SET bytea_output=’escape’ in yourdatabase.


Enhanced: 2.0.0 support for higher coordinate dimensions was introduced.

Enhanced: 2.0.0 support for specifying endian with geography was introduced.

Availability: 1.5.0 geography support was introduced.









Examples

SELECT ST_AsBinary(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326));

st_asbinary--------------------------------\001\003\000\000\000\001\000\000\000\005\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\360?\000\000\000\000\000\000\360?\000\000\000\000\000\000\360?\000\000\000\000\000\000\360?\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000(1 row)

SELECT ST_AsBinary(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326), ’XDR’);st_asbinary

--------------------------------\000\000\000\000\003\000\000\000\001\000\000\000\005\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000(1 row)

See Also

ST_GeomFromWKB ST_AsEWKB, ST_AsText,

8.6.2 ST_AsEWKB

ST_AsEWKB — Return the Well-Known Binary (WKB) representation of the geometry with SRID meta data.

Synopsis

bytea ST_AsEWKB(geometry g1);bytea ST_AsEWKB(geometry g1, text NDR_or_XDR);

Description

Returns the Well-Known Binary representation of the geometry with SRID metadata. There are 2 variants of the function.The first variant takes no endian encoding parameter and defaults to little endian. The second variant takes a second argumentdenoting the encoding - using little-endian (’NDR’) or big-endian (’XDR’) encoding.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

NoteThe WKB spec does not include the SRID. To get the OGC WKB format use ST_AsBinary


NoteST_AsEWKB is the reverse of ST_GeomFromEWKB. Use ST_GeomFromEWKB to convert to a postgis geometry fromST_AsEWKB representation.






Examples

SELECT ST_AsEWKB(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326));

st_asewkb--------------------------------\001\003\000\000 \346\020\000\000\001\000\000\000\005\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\360?\000\000\000\000\000\000\360?\000\000\000\000\000\000\360?\000\000\000\000\000\000\360?\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000(1 row)

SELECT ST_AsEWKB(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326), ’XDR’);st_asewkb

--------------------------------\000 \000\000\003\000\000\020\346\000\000\000\001\000\000\000\005\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000?\360\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000

See Also

ST_AsBinary, ST_AsEWKT, ST_AsText, ST_GeomFromEWKT, ST_SRID

8.6.3 ST_AsEWKT

ST_AsEWKT — Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.

Synopsis

text ST_AsEWKT(geometry g1);text ST_AsEWKT(geography g1);


Description

Returns the Well-Known Text representation of the geometry prefixed with the SRID.

NoteThe WKT spec does not include the SRID. To get the OGC WKT format use ST_AsText

WKT format does not maintain precision so to prevent floating truncation, use ST_AsBinary or ST_AsEWKB format fortransport.

NoteST_AsEWKT is the reverse of ST_GeomFromEWKT. Use ST_GeomFromEWKT to convert to a postgis geometry fromST_AsEWKT representation.

Enhanced: 2.0.0 support for Geography, Polyhedral surfaces, Triangles and TIN was introduced.





Examples

SELECT ST_AsEWKT(’0103000020E61000000100000005000000000000000000000000000000000000000000000000000000000000000000F03F000000000000F03F000000000000F03F000000000000F03F000000000000000000000000000000000000000000000000’::geometry);

st_asewkt--------------------------------SRID=4326;POLYGON((0 0,0 1,1 1,1 0,0 0))(1 row)

SELECT ST_AsEWKT(’0108000080030000000000000060 ←↩E30A4100000000785C0241000000000000F03F0000000018

E20A4100000000485F024100000000000000400000000018E20A4100000000305C02410000000000000840’)

--st_asewkt---CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)

See Also

ST_AsBinaryST_AsEWKBST_AsText, ST_GeomFromEWKT


8.6.4 ST_AsGeoJSON

ST_AsGeoJSON — Return the geometry as a GeoJSON element.

Synopsis

text ST_AsGeoJSON(geometry geom, integer maxdecimaldigits=15, integer options=0);text ST_AsGeoJSON(geography geog, integer maxdecimaldigits=15, integer options=0);text ST_AsGeoJSON(integer gj_version, geometry geom, integer maxdecimaldigits=15, integer options=0);text ST_AsGeoJSON(integer gj_version, geography geog, integer maxdecimaldigits=15, integer options=0);

Description

Return the geometry as a Geometry Javascript Object Notation (GeoJSON) element. (Cf GeoJSON specifications 1.0). 2D and3D Geometries are both supported. GeoJSON only support SFS 1.1 geometry type (no curve support for example).

The gj_version parameter is the major version of the GeoJSON spec. If specified, must be 1. This represents the spec version ofGeoJSON.

The third argument may be used to reduce the maximum number of decimal places used in output (defaults to 15).

The last ’options’ argument could be used to add Bbox or Crs in GeoJSON output:

• 0: means no option (default value)

• 1: GeoJSON Bbox

• 2: GeoJSON Short CRS (e.g EPSG:4326)

• 4: GeoJSON Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

Version 1: ST_AsGeoJSON(geom) / precision=15 version=1 options=0

Version 2: ST_AsGeoJSON(geom, precision) / version=1 options=0

Version 3: ST_AsGeoJSON(geom, precision, options) / version=1

Version 4: ST_AsGeoJSON(gj_version, geom) / precision=15 options=0

Version 5: ST_AsGeoJSON(gj_version, geom, precision) /options=0

Version 6: ST_AsGeoJSON(gj_version, geom, precision,options)

Availability: 1.3.4


Changed: 2.0.0 support default args and named args.


Examples

GeoJSON format is generally more efficient than other formats for use in ajax mapping. One popular javascript client thatsupports this is Open Layers. Example of its use is OpenLayers GeoJSON Example

SELECT ST_AsGeoJSON(the_geom) from fe_edges limit 1;st_asgeojson

----------------------------------------------------------------------------------------------------------- ←↩

{"type":"MultiLineString","coordinates":[[[-89.734634999999997,31.492072000000000],

http://geojson.org/geojson-spec.html

http://openlayers.org/dev/examples/vector-formats.html


[-89.734955999999997,31.492237999999997]]]}(1 row)--3d pointSELECT ST_AsGeoJSON(’LINESTRING(1 2 3, 4 5 6)’);

st_asgeojson-----------------------------------------------------------------------------------------{"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

8.6.5 ST_AsGML

ST_AsGML — Return the geometry as a GML version 2 or 3 element.

Synopsis

text ST_AsGML(geometry geom, integer maxdecimaldigits=15, integer options=0);text ST_AsGML(geography geog, integer maxdecimaldigits=15, integer options=0);text ST_AsGML(integer version, geometry geom, integer maxdecimaldigits=15, integer options=0, text nprefix=null);text ST_AsGML(integer version, geography geog, integer maxdecimaldigits=15, integer options=0, text nprefix=null);

Description

Return the geometry as a Geography Markup Language (GML) element. The version parameter, if specified, may be either 2 or3. If no version parameter is specified then the default is assumed to be 2. The precision argument may be used to reduce themaximum number of decimal places (maxdecimaldigits) used in output (defaults to 15).

GML 2 refer to 2.1.2 version, GML 3 to 3.1.1 version

The ’options’ argument is a bitfield. It could be used to define CRS output type in GML output, and to declare data as lat/lon:

• 0: GML Short CRS (e.g EPSG:4326), default value

• 1: GML Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

• 2: For GML 3 only, remove srsDimension attribute from output.

• 4: For GML 3 only, use <LineString> rather than <Curve> tag for lines.

• 16: Declare that datas are lat/lon (e.g srid=4326). Default is to assume that data are planars. This option is useful for GML3.1.1 output only, related to axis order. So if you set it, it will swap the coordinates so order is lat lon instead of database lonlat.

• 32: Output the box of the geometry (envelope).

The ’namespace prefix’ argument may be used to specify a custom namespace prefix or no prefix (if empty). If null or omitted’gml’ prefix is used

Availability: 1.3.2


Enhanced: 2.0.0 prefix support was introduced. Option 4 for GML3 was introduced to allow using LineString instead of Curvetag for lines. GML3 Support for Polyhedral surfaces and TINS was introduced. Option 32 was introduced to output the box.

Changed: 2.0.0 use default named args


NoteOnly version 3+ of ST_AsGML supports Polyhedral Surfaces and TINS.




Examples: Version 2

SELECT ST_AsGML(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326));st_asgml--------<gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates ←↩

>0,0 0,1 1,1 1,0 0,0</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml: ←↩Polygon>

Examples: Version 3

-- Flip coordinates and output extended EPSG (16 | 1)--SELECT ST_AsGML(3, ST_GeomFromText(’POINT(5.234234233242 6.34534534534)’,4326), 5, 17);

st_asgml--------

<gml:Point srsName="urn:ogc:def:crs:EPSG::4326"><gml:pos>6.34535 5.23423</gml:pos></gml ←↩:Point>

-- Output the envelope (32) --SELECT ST_AsGML(3, ST_GeomFromText(’LINESTRING(1 2, 3 4, 10 20)’,4326), 5, 32);

st_asgml--------

<gml:Envelope srsName="EPSG:4326"><gml:lowerCorner>1 2</gml:lowerCorner><gml:upperCorner>10 20</gml:upperCorner>

</gml:Envelope>

-- Output the envelope (32) , reverse (lat lon instead of lon lat) (16), long srs (1)= 32 | ←↩16 | 1 = 49 --

SELECT ST_AsGML(3, ST_GeomFromText(’LINESTRING(1 2, 3 4, 10 20)’,4326), 5, 49);st_asgml--------

<gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326"><gml:lowerCorner>2 1</gml:lowerCorner><gml:upperCorner>20 10</gml:upperCorner>

</gml:Envelope>

-- Polyhedral Example --SELECT ST_AsGML(3, ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0) ←↩

),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’));


st_asgml--------

<gml:PolyhedralSurface><gml:polygonPatches>

<gml:PolygonPatch><gml:exterior>

<gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList>

</gml:LinearRing></gml:exterior></gml:PolygonPatch><gml:PolygonPatch><gml:exterior>










</gml:LinearRing></gml:exterior></gml:PolygonPatch>

</gml:polygonPatches></gml:PolyhedralSurface>

See Also

ST_GeomFromGML

8.6.6 ST_AsHEXEWKB

ST_AsHEXEWKB — Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR)encoding.


Synopsis

text ST_AsHEXEWKB(geometry g1, text NDRorXDR);text ST_AsHEXEWKB(geometry g1);

Description

Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding. If noencoding is specified, then NDR is used.

NoteAvailability: 1.2.2



Examples

SELECT ST_AsHEXEWKB(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326));which gives same answer as

SELECT ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326)::text;

st_ashexewkb--------0103000020E61000000100000005000000000000000000000000000000000000000000000000000000000000000000F03F000000000000F03F000000000000F03F000000000000F03F000000000000000000000000000000000000000000000000

8.6.7 ST_AsKML

ST_AsKML — Return the geometry as a KML element. Several variants. Default version=2, default precision=15

Synopsis

text ST_AsKML(geometry geom, integer maxdecimaldigits=15);text ST_AsKML(geography geog, integer maxdecimaldigits=15);text ST_AsKML(integer version, geometry geom, integer maxdecimaldigits=15, text nprefix=NULL);text ST_AsKML(integer version, geography geog, integer maxdecimaldigits=15, text nprefix=NULL);

Description

Return the geometry as a Keyhole Markup Language (KML) element. There are several variants of this function. maximumnumber of decimal places used in output (defaults to 15), version default to 2 and default namespace is no prefix.

Version 1: ST_AsKML(geom_or_geog, maxdecimaldigits) / version=2 / maxdecimaldigits=15

Version 2: ST_AsKML(version, geom_or_geog, maxdecimaldigits, nprefix) maxdecimaldigits=15 / nprefix=NULL


NoteRequires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiledin.

NoteAvailability: 1.2.2 - later variants that include version param came in 1.3.2

NoteEnhanced: 2.0.0 - Add prefix namespace. Default is no prefix

NoteChanged: 2.0.0 - uses default args and supports named args

NoteAsKML output will not work with geometries that do not have an SRID


Examples

SELECT ST_AsKML(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326));

st_askml--------<Polygon><outerBoundaryIs><LinearRing><coordinates>0,0 0,1 1,1 1,0 0,0</coordinates></ ←↩

LinearRing></outerBoundaryIs></Polygon>

--3d linestringSELECT ST_AsKML(’SRID=4326;LINESTRING(1 2 3, 4 5 6)’);<LineString><coordinates>1,2,3 4,5,6</coordinates></LineString>

See Also

ST_AsSVG, ST_AsGML

8.6.8 ST_AsSVG

ST_AsSVG — Returns a Geometry in SVG path data given a geometry or geography object.


Synopsis

text ST_AsSVG(geometry geom, integer rel=0, integer maxdecimaldigits=15);text ST_AsSVG(geography geog, integer rel=0, integer maxdecimaldigits=15);

Description

Return the geometry as Scalar Vector Graphics (SVG) path data. Use 1 as second argument to have the path data implementedin terms of relative moves, the default (or 0) uses absolute moves. Third argument may be used to reduce the maximum numberof decimal digits used in output (defaults to 15). Point geometries will be rendered as cx/cy when ’rel’ arg is 0, x/y when ’rel’ is1. Multipoint geometries are delimited by commas (","), GeometryCollection geometries are delimited by semicolons (";").

NoteAvailability: 1.2.2. Availability: 1.4.0 Changed in PostGIS 1.4.0 to include L command in absolute path to conform tohttp://www.w3.org/TR/SVG/paths.html#PathDataBNF

Changed: 2.0.0 to use default args and support named args

Examples

SELECT ST_AsSVG(ST_GeomFromText(’POLYGON((0 0,0 1,1 1,1 0,0 0))’,4326));

st_assvg--------M 0 0 L 0 -1 1 -1 1 0 Z

8.6.9 ST_AsX3D

ST_AsX3D — Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML

Synopsis

text ST_AsX3D(geometry g1, integer maxdecimaldigits=15, integer options=0);

Description

Returns a geometry as an X3D xml formatted node element http://web3d.org/x3d/specifications/ISO-IEC-19776-1.2-X3DEncodings-XML/Part01/EncodingOfNodes.html. If maxdecimaldigits (precision) is not specified then defaults to 15.

NoteThere are various options for translating PostGIS geometries to X3D since X3D geometry types don’t map directlyto PostGIS geometry types and some newer X3D types that might be better mappings we ahve avoided since mostrendering tools don’t currently support them. These are the mappings we have settled on. Feel free to post a bug ticketif you have thoughts on the idea or ways we can allow people to denote their preferred mappings.Below is how we currently map PostGIS 2D/3D types to X3D types

http://www.w3.org/TR/SVG/paths.html#PathDataBNF

http://web3d.org/x3d/specifications/ISO-IEC-19776-1.2-X3DEncodings-XML/Part01/EncodingOfNodes.html

http://web3d.org/x3d/specifications/ISO-IEC-19776-1.2-X3DEncodings-XML/Part01/EncodingOfNodes.html


PostGIS Type 2D X3D Type 3D X3D Type

PostGIS Type 2D X3D Type 3D X3D Type

LINESTRING not yet implemented - will bePolyLine2D LineSet

MULTILINESTRING not yet implemented - will bePolyLine2D IndexedLineSet

MULTIPOINT Polypoint2D PointSet

POINT outputs the space delimitedcoordinates

outputs the space delimitedcoordinates

(MULTI) POLYGON,POLYHEDRALSURFACE Invalid X3D markup IndexedFaceSet (inner rings currently

output as another faceset)TIN TriangleSet2D (Not Yet Implemented) IndexedTriangleSet

Note2D geometry support not yet complete. Inner rings currently just drawn as separate polygons. We are working onthese.

Lots of advancements happening in 3D space particularly with X3D Integration with HTML5

There is also a nice open source X3D viewer you can use to view rendered geometries. Free Wrl http://freewrl.sourceforge.net/binaries available for Mac, Linux, and Windows. Use the FreeWRL_Launcher packaged to view the geometries.

Availability: 2.0.0: ISO-IEC-19776-1.2-X3DEncodings-XML




Example: Create a fully functional X3D document - This will generate a cube that is viewable in FreeWrl and other X3Dviewers.

SELECT ’<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d ←↩

-3.0.dtd"><X3D>

<Scene><Transform>

<Shape><Appearance>

<Material emissiveColor=’’0 0 1’’/></Appearance> ’ ||ST_AsX3D( ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),

((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’)) ||

’</Shape></Transform>

</Scene></X3D>’ As x3ddoc;

x3ddoc

http://www.web3d.org/x3d/wiki/index.php/X3D_and_HTML5#Goals:_X3D_and_HTML5

http://freewrl.sourceforge.net/


--------<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d ←↩

-3.0.dtd"><X3D>

<Scene><Transform>

<Shape><Appearance>

<Material emissiveColor=’0 0 1’/></Appearance><IndexedFaceSet coordIndex=’0 1 2 3 -1 4 5 6 7 -1 8 9 10 11 -1 12 13 14 15 -1 16 17 ←↩

18 19 -1 20 21 22 23’><Coordinate point=’0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 0 ←↩

1 0 1 0 0 1 1 1 0 1 1 1 1 0 1 1 0 0 0 1 0 0 1 1 1 1 1 1 1 0 0 0 1 1 0 1 1 1 ←↩1 0 1 1’ />

</IndexedFaceSet></Shape>

</Transform></Scene>

</X3D>

Example: An Octagon elevated 3 Units and decimal precision of 6

SELECT ST_AsX3D(ST_Translate(

ST_Force_3d(ST_Buffer(ST_Point(10,10),5, ’quad_segs=2’)), 0,0,

3),6) As x3dfrag;

x3dfrag--------<IndexedFaceSet coordIndex="0 1 2 3 4 5 6 7">

<Coordinate point="15 10 3 13.535534 6.464466 3 10 5 3 6.464466 6.464466 3 5 10 3 ←↩6.464466 13.535534 3 10 15 3 13.535534 13.535534 3 " />

</IndexedFaceSet>

Example: TIN

SELECT ST_AsX3D(ST_GeomFromEWKT(’TIN (((0 0 0,0 0 1,0 1 0,0 0 0

)), ((0 0 0,0 1 0,1 1 0,0 0 0

)))’)) As x3dfrag;

x3dfrag--------

<IndexedTriangleSet index=’0 1 2 3 4 5’><Coordinate point=’0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 ←↩1 0’/></IndexedTriangleSet>


Example: Closed multilinestring (the boundary of a polygon with holes)

SELECT ST_AsX3D(ST_GeomFromEWKT(’MULTILINESTRING((20 0 10,16 -12 10,0 -16 10,-12 -12 10,-20 0 ←↩

10,-12 16 10,0 24 10,16 16 10,20 0 10),(12 0 10,8 8 10,0 12 10,-8 8 10,-8 0 10,-8 -4 10,0 -8 10,8 -4 10,12 0 10))’)

) As x3dfrag;

x3dfrag--------

<IndexedLineSet coordIndex=’0 1 2 3 4 5 6 7 0 -1 8 9 10 11 12 13 14 15 8’><Coordinate point=’20 0 10 16 -12 10 0 -16 10 -12 -12 10 -20 0 10 -12 16 10 0 24 10 16 ←↩

16 10 12 0 10 8 8 10 0 12 10 -8 8 10 -8 0 10 -8 -4 10 0 -8 10 8 -4 10 ’ /></IndexedLineSet>

8.6.10 ST_GeoHash

ST_GeoHash — Return a GeoHash representation (geohash.org) of the geometry.

Synopsis

text ST_GeoHash(geometry geom, integer maxchars=full_precision_of_point);

Description

Return a GeoHash representation (geohash.org) of the geometry. A GeoHash encodes a point into a text form that is sortable andsearchable based on prefixing. A shorter GeoHash is a less precise representation of a point. It can also be thought of as a box,that contains the actual point.

If no maxchars is specficified ST_GeoHash returns a GeoHash based on full precision of the input geometry type. Points returna GeoHash with 20 characters of precision (about enough to hold the full double precision of the input). Other types return aGeoHash with a variable amount of precision, based on the size of the feature. Larger features are represented with less precision,smaller features with more precision. The idea is that the box implied by the GeoHash will always contain the input feature.

If maxchars is specified ST_GeoHash returns a GeoHash with at most that many characters so a possibly lower precisionrepresentation of the input geometry. For non-points, the starting point of the calculation is the center of the bounding box of thegeometry.

Availability: 1.4.0

NoteST_GeoHash will not work with geometries that are not in geographic (lon/lat) coordinates.


Examples

SELECT ST_GeoHash(ST_SetSRID(ST_MakePoint(-126,48),4326));

st_geohash----------------------c0w3hf1s70w3hf1s70w3


SELECT ST_GeoHash(ST_SetSRID(ST_MakePoint(-126,48),4326),5);

st_geohash------------c0w3h

See Also

8.6.11 ST_AsText

ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

Synopsis

text ST_AsText(geometry g1);text ST_AsText(geography g1);

Description

Returns the Well-Known Text representation of the geometry/geography.

NoteThe WKT spec does not include the SRID. To get the SRID as part of the data, use the non-standard PostGISST_AsEWKT

WKT format does not maintain precision so to prevent floating truncation, use ST_AsBinary or ST_AsEWKB format fortransport.

NoteST_AsText is the reverse of ST_GeomFromText. Use ST_GeomFromText to convert to a postgis geometry fromST_AsText representation.

Availability: 1.5 - support for geography was introduced.






Examples

SELECT ST_AsText(’01030000000100000005000000000000000000000000000000000000000000000000000000000000000000F03F000000000000F03F000000000000F03F000000000000F03F000000000000000000000000000000000000000000000000’);

st_astext--------------------------------POLYGON((0 0,0 1,1 1,1 0,0 0))

(1 row)

See Also

ST_AsBinary, ST_AsEWKB, ST_AsEWKT, ST_GeomFromText

8.6.12 ST_AsLatLonText

ST_AsLatLonText — Return the Degrees, Minutes, Seconds representation of the given point.

Synopsis

text ST_AsLatLonText(geometry pt);text ST_AsLatLonText(geometry pt, text format);

Description

Returns the Degrees, Minutes, Seconds representation of the point.

NoteIt is assumed the point is in a lat/lon projection. The X (lon) and Y (lat) coordinates are normalized in the output to the"normal" range (-180 to +180 for lon, -90 to +90 for lat).

The text parameter is a format string containing the format for the resulting text, similar to a date format string. Valid tokensare "D" for degrees, "M" for minutes, "S" for seconds, and "C" for cardinal direction (NSEW). DMS tokens may be repeated toindicate desired width and precision ("SSS.SSSS" means " 1.0023").

"M", "S", and "C" are optional. If "C" is omitted, degrees are shown with a "-" sign if south or west. If "S" is omitted, minuteswill be shown as decimal with as many digits of precision as you specify. If "M" is also omitted, degrees are shown as decimalwith as many digits precision as you specify.

If the format string is omitted (or zero-length) a default format will be used.

Availability: 2.0

Examples

Default format.

SELECT (ST_AsLatLonText(’POINT (-3.2342342 -2.32498)’));st_aslatlontext

----------------------------2\textdegree{}19’29.928"S 3\textdegree{}14’3.243"W


Providing a format (same as the default).

SELECT (ST_AsLatLonText(’POINT (-3.2342342 -2.32498)’, ’D\textdegree{}M’’S.SSS"C’));st_aslatlontext

----------------------------2\textdegree{}19’29.928"S 3\textdegree{}14’3.243"W

Characters other than D, M, S, C and . are just passed through.

SELECT (ST_AsLatLonText(’POINT (-3.2342342 -2.32498)’, ’D degrees, M minutes, S seconds to ←↩the C’));

st_aslatlontext--------------------------------------------------------------------------------------2 degrees, 19 minutes, 30 seconds to the S 3 degrees, 14 minutes, 3 seconds to the W

Signed degrees instead of cardinal directions.

SELECT (ST_AsLatLonText(’POINT (-3.2342342 -2.32498)’, ’D\textdegree{}M’’S.SSS"’));st_aslatlontext

-----------------------------2\textdegree{}19’29.928" -3\textdegree{}14’3.243"

Decimal degrees.

SELECT (ST_AsLatLonText(’POINT (-3.2342342 -2.32498)’, ’D.DDDD degrees C’));st_aslatlontext

-----------------------------------2.3250 degrees S 3.2342 degrees W

Excessively large values are normalized.

SELECT (ST_AsLatLonText(’POINT (-302.2342342 -792.32498)’));st_aslatlontext

-------------------------------72\textdegree{}19’29.928"S 57\textdegree{}45’56.757"E

8.7 Operators

8.7.1 &&

&& — Returns TRUE if A’s 2D bounding box intersects B’s 2D bounding box.

Synopsis

boolean &&( geometry A , geometry B );boolean &&( geography A , geography B );

Description

The && operator returns TRUE if the 2D bounding box of geometry A intersects the 2D bounding box of geometry B.

NoteThis operand will make use of any indexes that may be available on the geometries.



Availability: 1.5.0 support for geography was introduced.



Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 && tbl2.column2 AS overlapsFROM ( VALUES

(1, ’LINESTRING(0 0, 3 3)’::geometry),(2, ’LINESTRING(0 1, 0 5)’::geometry)) AS tbl1,

( VALUES(3, ’LINESTRING(1 2, 4 6)’::geometry)) AS tbl2;

column1 | column1 | overlaps---------+---------+----------

1 | 3 | t2 | 3 | f

(2 rows)

See Also

|&>, &>, &<|, &<, ~, @

8.7.2 &&&

&&& — Returns TRUE if A’s 3D bounding box intersects B’s 3D bounding box.

Synopsis

boolean &&&( geometry A , geometry B );

Description

The &&& operator returns TRUE if the n-D bounding box of geometry A intersects the n-D bounding box of geometry B.


Availability: 2.0.0






Examples: 3D LineStrings

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3d,tbl1.column2 && tbl2.column2 AS overlaps_2d

FROM ( VALUES(1, ’LINESTRING Z(0 0 1, 3 3 2)’::geometry),(2, ’LINESTRING Z(1 2 0, 0 5 -1)’::geometry)) AS tbl1,

( VALUES(3, ’LINESTRING Z(1 2 1, 4 6 1)’::geometry)) AS tbl2;

column1 | column1 | overlaps_3d | overlaps_2d---------+---------+-------------+-------------

1 | 3 | t | t2 | 3 | f | t

Examples: 3M LineStrings

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3zm,tbl1.column2 && tbl2.column2 AS overlaps_2d

FROM ( VALUES(1, ’LINESTRING M(0 0 1, 3 3 2)’::geometry),(2, ’LINESTRING M(1 2 0, 0 5 -1)’::geometry)) AS tbl1,

( VALUES(3, ’LINESTRING M(1 2 1, 4 6 1)’::geometry)) AS tbl2;

column1 | column1 | overlaps_3zm | overlaps_2d---------+---------+-------------+-------------

1 | 3 | t | t2 | 3 | f | t

See Also

&&

8.7.3 &<

&< — Returns TRUE if A’s bounding box overlaps or is to the left of B’s.

Synopsis

boolean &<( geometry A , geometry B );

Description

The &< operator returns TRUE if the bounding box of geometry A overlaps or is to the left of the bounding box of geometry B,or more accurately, overlaps or is NOT to the right of the bounding box of geometry B.



Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &< tbl2.column2 AS overleftFROM

( VALUES(1, ’LINESTRING(1 2, 4 6)’::geometry)) AS tbl1,( VALUES(2, ’LINESTRING(0 0, 3 3)’::geometry),(3, ’LINESTRING(0 1, 0 5)’::geometry),(4, ’LINESTRING(6 0, 6 1)’::geometry)) AS tbl2;

column1 | column1 | overleft---------+---------+----------

1 | 2 | f1 | 3 | f1 | 4 | t

(3 rows)

See Also

&&, |&>, &>, &<|

8.7.4 &<|

&<| — Returns TRUE if A’s bounding box overlaps or is below B’s.

Synopsis

boolean &<|( geometry A , geometry B );

Description

The &<| operator returns TRUE if the bounding box of geometry A overlaps or is below of the bounding box of geometry B, ormore accurately, overlaps or is NOT above the bounding box of geometry B.




Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &<| tbl2.column2 AS overbelowFROM

( VALUES(1, ’LINESTRING(6 0, 6 4)’::geometry)) AS tbl1,( VALUES(2, ’LINESTRING(0 0, 3 3)’::geometry),


(3, ’LINESTRING(0 1, 0 5)’::geometry),(4, ’LINESTRING(1 2, 4 6)’::geometry)) AS tbl2;

column1 | column1 | overbelow---------+---------+-----------

1 | 2 | f1 | 3 | t1 | 4 | t

(3 rows)

See Also

&&, |&>, &>, &<

8.7.5 &>

&> — Returns TRUE if A’ bounding box overlaps or is to the right of B’s.

Synopsis

boolean &>( geometry A , geometry B );

Description

The &> operator returns TRUE if the bounding box of geometry A overlaps or is to the right of the bounding box of geometry B,or more accurately, overlaps or is NOT to the left of the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 &> tbl2.column2 AS overrightFROM


column1 | column1 | overright---------+---------+-----------

1 | 2 | t1 | 3 | t1 | 4 | f

(3 rows)

See Also

&&, |&>, &<|, &<


8.7.6 <<

<< — Returns TRUE if A’s bounding box is strictly to the left of B’s.

Synopsis

boolean <<( geometry A , geometry B );

Description

The << operator returns TRUE if the bounding box of geometry A is strictly to the left of the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 << tbl2.column2 AS leftFROM

( VALUES(1, ’LINESTRING (1 2, 1 5)’::geometry)) AS tbl1,( VALUES(2, ’LINESTRING (0 0, 4 3)’::geometry),(3, ’LINESTRING (6 0, 6 5)’::geometry),(4, ’LINESTRING (2 2, 5 6)’::geometry)) AS tbl2;

column1 | column1 | left---------+---------+------

1 | 2 | f1 | 3 | t1 | 4 | t

(3 rows)

See Also

>>, |>>, <<|

8.7.7 <<|

<<| — Returns TRUE if A’s bounding box is strictly below B’s.

Synopsis

boolean <<|( geometry A , geometry B );


Description

The <<| operator returns TRUE if the bounding box of geometry A is strictly below the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 <<| tbl2.column2 AS belowFROM


column1 | column1 | below---------+---------+-------

1 | 2 | t1 | 3 | f1 | 4 | f

(3 rows)

See Also

<<, >>, |>>

8.7.8 =

= — Returns TRUE if A’s bounding box is the same as B’s. Uses double precision bounding box.

Synopsis

boolean =( geometry A , geometry B );boolean =( geography A , geography B );

Description

The = operator returns TRUE if the bounding box of geometry/geography A is the same as the bounding box of geometry/geog-raphy B. PostgreSQL uses the =, <, and > operators defined for geometries to perform internal orderings and comparison ofgeometries (ie. in a GROUP BY or ORDER BY clause).

WarningThis is cause for a lot of confusion. When you compare geometryA = geometryB it will return true even when thegeometries are clearly different IF their bounding boxes are the same. To check for true equality use ST_OrderingEqualsor ST_Equals


CautionThis operand will NOT make use of any indexes that may be available on the geometries.



Changed: 2.0.0 , the bounding box of geometries was changed to use double precision instead of float4 precision of prior. Theside effect of this is that in particular points in prior versions that were a little different may have returned true in prior versionsand false in 2.0+ since their float4 boxes would be the same but there float8 (double precision), would be different.

Examples

SELECT ’LINESTRING(0 0, 0 1, 1 0)’::geometry = ’LINESTRING(1 1, 0 0)’::geometry;?column?

----------t

(1 row)

SELECT ST_AsText(column1)FROM ( VALUES

(’LINESTRING(0 0, 1 1)’::geometry),(’LINESTRING(1 1, 0 0)’::geometry)) AS foo;st_astext

---------------------LINESTRING(0 0,1 1)LINESTRING(1 1,0 0)

(2 rows)

-- Note: the GROUP BY uses the "=" to compare for geometry equivalency.SELECT ST_AsText(column1)FROM ( VALUES

(’LINESTRING(0 0, 1 1)’::geometry),(’LINESTRING(1 1, 0 0)’::geometry)) AS foo

GROUP BY column1;st_astext

---------------------LINESTRING(0 0,1 1)

(1 row)

-- In versions prior to 2.0, this used to return true --SELECT ST_GeomFromText(’POINT(1707296.37 4820536.77)’) =ST_GeomFromText(’POINT(1707296.27 4820536.87)’) As pt_intersect;

--pt_intersect --f

See Also

ST_Equals, ST_OrderingEquals

8.7.9 >>

>> — Returns TRUE if A’s bounding box is strictly to the right of B’s.


Synopsis

boolean >>( geometry A , geometry B );

Description

The >> operator returns TRUE if the bounding box of geometry A is strictly to the right of the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 >> tbl2.column2 AS rightFROM


column1 | column1 | right---------+---------+-------

1 | 2 | t1 | 3 | f1 | 4 | f

(3 rows)

See Also

<<, |>>, <<|

8.7.10 @

@ — Returns TRUE if A’s bounding box is contained by B’s.

Synopsis

boolean @( geometry A , geometry B );

Description

The @ operator returns TRUE if the bounding box of geometry A is completely contained by the bounding box of geometry B.



Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 @ tbl2.column2 AS containedFROM


column1 | column1 | contained---------+---------+-----------

1 | 2 | t1 | 3 | f1 | 4 | t

(3 rows)

See Also

~, &&

8.7.11 |&>

|&> — Returns TRUE if A’s bounding box overlaps or is above B’s.

Synopsis

boolean |&>( geometry A , geometry B );

Description

The |&> operator returns TRUE if the bounding box of geometry A overlaps or is above the bounding box of geometry B, ormore accurately, overlaps or is NOT below the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 |&> tbl2.column2 AS overaboveFROM


column1 | column1 | overabove---------+---------+-----------

1 | 2 | t


1 | 3 | f1 | 4 | f

(3 rows)

See Also

&&, &>, &<|, &<

8.7.12 |>>

|>> — Returns TRUE if A’s bounding box is strictly above B’s.

Synopsis

boolean |>>( geometry A , geometry B );

Description

The |>> operator returns TRUE if the bounding box of geometry A is strictly to the right of the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 |>> tbl2.column2 AS aboveFROM


column1 | column1 | above---------+---------+-------

1 | 2 | t1 | 3 | f1 | 4 | f

(3 rows)

See Also

<<, >>, <<|

8.7.13 ~

~ — Returns TRUE if A’s bounding box contains B’s.


Synopsis

boolean ~( geometry A , geometry B );

Description

The ~ operator returns TRUE if the bounding box of geometry A completely contains the bounding box of geometry B.


Examples

SELECT tbl1.column1, tbl2.column1, tbl1.column2 ~ tbl2.column2 AS containsFROM


column1 | column1 | contains---------+---------+----------

1 | 2 | f1 | 3 | t1 | 4 | t

(3 rows)

See Also

@, &&

8.7.14 ~=

~= — Returns TRUE if A’s bounding box is the same as B’s.

Synopsis

boolean ~=( geometry A , geometry B );

Description

The ~= operator returns TRUE if the bounding box of geometry/geography A is the same as the bounding box of geometry/geog-raphy B.



Availability: 1.5.0 changed behavior


WarningThis operator has changed behavior in PostGIS 1.5 from testing for actual geometric equality to only checking forbounding box equality. To complicate things it also depends on if you have done a hard or soft upgrade which behavioryour database has. To find out which behavior your database has you can run the query below. To check for trueequality use ST_OrderingEquals or ST_Equals and to check for bounding box equality =; operator is a safer option.

Examples

select ’LINESTRING(0 0, 1 1)’::geometry ~= ’LINESTRING(0 1, 1 0)’::geometry as equality;equality |

-----------------+t |

The above can be used to test if you have the new or old behavior of ~= operator.

See Also

ST_Equals, ST_OrderingEquals, =

8.7.15 <->

<-> — Returns the distance between two points. For point / point checks it uses floating point accuracy (as opposed to the doubleprecision accuracy of the underlying point geometry). For other geometry types the distance between the floating point boundingbox centroids is returned. Useful for doing distance ordering and nearest neighbor limits using KNN gist functionality.

Synopsis

double precision <->( geometry A , geometry B );

Description

The <-> operator returns distance between two points read from the spatial index for points (float precision). For other geometriesit returns the distance from centroid of bounding box of geometries. Useful for doing nearest neighbor approximate distanceordering.

NoteThis operand will make use of any indexes that may be available on the geometries. It is different from other operatorsthat use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

NoteIndex only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. ’SRID=3005;POINT(1011102450541)’::geometry instead of a.geom

Refer to OpenGeo workshop: Nearest-Neighbour Searching for real live example.

Availability: 2.0.0 only available for PostgreSQL 9.1+

http://workshops.opengeo.org/postgis-intro/knn.html


Examples

SELECT ST_Distance(geom, ’SRID=3005;POINT(1011102 450541)’::geometry) as d,edabbr, vaabbrFROM va2005ORDER BY d limit 10;

d | edabbr | vaabbr------------------+--------+--------

0 | ALQ | 1285541.57712511724 | ALQ | 129A5579.67450712005 | ALQ | 0016083.4207708641 | ALQ | 1317691.2205404848 | ALQ | 003

7900.75451037313 | ALQ | 1228694.20710669982 | ALQ | 129B9564.24289057111 | ALQ | 13012089.665931705 | ALQ | 127

18472.5531479404 | ALQ | 002(10 rows)

Then the KNN raw answer:

SELECT st_distance(geom, ’SRID=3005;POINT(1011102 450541)’::geometry) as d,edabbr, vaabbrFROM va2005ORDER BY geom <-> ’SRID=3005;POINT(1011102 450541)’::geometry limit 10;

d | edabbr | vaabbr------------------+--------+--------

0 | ALQ | 1285579.67450712005 | ALQ | 0015541.57712511724 | ALQ | 129A8694.20710669982 | ALQ | 129B9564.24289057111 | ALQ | 1306083.4207708641 | ALQ | 13112089.665931705 | ALQ | 12724795.264503022 | ALQ | 124

24587.6584922302 | ALQ | 12326764.2555463114 | ALQ | 125

(10 rows)

Note the misordering in the actual distances and the different entries that actually show up in the top 10.

Finally the hybrid:

WITH index_query AS (SELECT ST_Distance(geom, ’SRID=3005;POINT(1011102 450541)’::geometry) as d,edabbr, vaabbrFROM va2005

ORDER BY geom <-> ’SRID=3005;POINT(1011102 450541)’::geometry LIMIT 100)SELECT *FROM index_query

ORDER BY d limit 10;

d | edabbr | vaabbr------------------+--------+--------

0 | ALQ | 1285541.57712511724 | ALQ | 129A5579.67450712005 | ALQ | 0016083.4207708641 | ALQ | 1317691.2205404848 | ALQ | 003

7900.75451037313 | ALQ | 1228694.20710669982 | ALQ | 129B9564.24289057111 | ALQ | 130


12089.665931705 | ALQ | 12718472.5531479404 | ALQ | 002

(10 rows)

See Also

ST_DWithin, ST_Distance, <#>

8.7.16 <#>

<#> — Returns the distance between bounding box of 2 geometries. For point / point checks it’s almost the same as distance(though may be different since the bounding box is at floating point accuracy and geometries are double precision). Useful fordoing distance ordering and nearest neighbor limits using KNN gist functionality.

Synopsis

double precision <#>( geometry A , geometry B );

Description

The <#>KNN GIST operator returns distance between two floating point bounding boxes read from the spatial index if available.Useful for doing nearest neighbor approximate distance ordering.

NoteThis operand will make use of any indexes that may be available on the geometries. It is different from other operatorsthat use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

NoteIndex only kicks in if one of the geometries is a constant e.g. ORDER BY (ST_GeomFromText(’POINT(1 2)’) <#> geom)instead of g1.geom <#>.

Availability: 2.0.0 only available for PostgreSQL 9.1+

Examples

SELECT *FROM (SELECT b.tlid, b.mtfcc,

b.geom <#> ST_GeomFromText(’LINESTRING(746149 2948672,745954 2948576,745787 2948499,745740 2948468,745712 2948438,745690 2948384,745677 2948319)’,2249) As b_dist,ST_Distance(b.geom, ST_GeomFromText(’LINESTRING(746149 2948672,745954 2948576,745787 2948499,745740 2948468,745712 2948438,745690 2948384,745677 2948319)’,2249)) As act_distFROM bos_roads As bORDER BY b_dist, b.tlidLIMIT 100) As fooORDER BY act_dist, tlid LIMIT 10;


tlid | mtfcc | b_dist | act_dist-----------+-------+------------------+------------------

85732027 | S1400 | 0 | 085732029 | S1400 | 0 | 085732031 | S1400 | 0 | 085734335 | S1400 | 0 | 085736037 | S1400 | 0 | 0

624683742 | S1400 | 0 | 128.52887426866685719343 | S1400 | 260.839270432962 | 260.83927043296285741826 | S1400 | 164.759294123275 | 260.83927043296285732032 | S1400 | 277.75 | 311.83028236526485735592 | S1400 | 222.25 | 311.830282365264

(10 rows)

See Also

ST_DWithin, ST_Distance, <->

8.8 Spatial Relationships and Measurements

8.8.1 ST_3DClosestPoint

ST_3DClosestPoint — Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line.

Synopsis

geometry ST_3DClosestPoint(geometry g1, geometry g2);

Description

Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line. The 3D length of the3D shortest line is the 3D distance.



Availability: 2.0.0

Examples


linestring and point -- both 3d and 2d closest point

SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt

FROM (SELECT ’POINT(100 100 30)’::geometry As pt,’LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)’:: ←↩

geometry As line) As foo;

cp3d_line_pt | ←↩cp2d_line_pt

-----------------------------------------------------------+------------------------------------------ ←↩

POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(73.0769230769231 ←↩115.384615384615)

linestring and multipoint -- both 3d and 2d closest point

SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt

FROM (SELECT ’MULTIPOINT(100 100 30, 50 74 1000)’::geometry As pt,’LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)’:: ←↩


cp3d_line_pt | cp2d_line_pt-----------------------------------------------------------+--------------POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(50 75)

Multilinestring and polygon both 3d and 2d closest point

SELECT ST_AsEWKT(ST_3DClosestPoint(poly, mline)) As cp3d,ST_AsEWKT(ST_ClosestPoint(poly, mline)) As cp2d

FROM (SELECT ST_GeomFromEWKT(’POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, ←↩100 100 5, 175 150 5))’) As poly,

ST_GeomFromEWKT(’MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 ←↩100 1, 175 155 1),

(1 10 2, 5 20 1))’) As mline ) As foo;cp3d | cp2d

-------------------------------------------+--------------POINT(39.993580415989 54.1889925532825 5) | POINT(20 40)

See Also

ST_AsEWKT, ST_ClosestPoint, ST_3DDistance, ST_3DShortestLine

8.8.2 ST_3DDistance

ST_3DDistance — For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between twogeometries in projected units.

Synopsis

float ST_3DDistance(geometry g1, geometry g2);


Description

For geometry type returns the 3-dimensional minimum cartesian distance between two geometries in projected units (spatial refunits).



This method implements the SQL/MM specification. SQL-MM ?

Availability: 2.0.0

Examples

-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point ←↩and line compared 2D point and line)

-- Note: currently no vertical datum support so Z is not transformed and assumed to be same ←↩units as final.

SELECT ST_3DDistance(ST_Transform(ST_GeomFromEWKT(’SRID=4326;POINT(-72.1235 42.3521 4)’),2163),ST_Transform(ST_GeomFromEWKT(’SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 ←↩

20)’),2163)) As dist_3d,ST_Distance(

ST_Transform(ST_GeomFromText(’POINT(-72.1235 42.3521)’,4326),2163),ST_Transform(ST_GeomFromText(’LINESTRING(-72.1260 42.45, -72.123 42.1546)’, 4326) ←↩

,2163)) As dist_2d;

dist_3d | dist_2d------------------+-----------------127.295059324629 | 126.66425605671

-- Multilinestring and polygon both 3d and 2d distance-- Same example as 3D closest point exampleSELECT ST_3DDistance(poly, mline) As dist3d,

ST_Distance(poly, mline) As dist2dFROM (SELECT ST_GeomFromEWKT(’POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 ←↩

100 5, 175 150 5))’) As poly,ST_GeomFromEWKT(’MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, ←↩

175 155 1),(1 10 2, 5 20 1))’) As mline ) As foo;

dist3d | dist2d-------------------+--------0.716635696066337 | 0

See Also

ST_Distance, ST_3DClosestPoint, ST_3DDWithin, ST_3DMaxDistance, ST_3DShortestLine, ST_Transform

8.8.3 ST_3DDWithin

ST_3DDWithin — For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.


Synopsis

boolean ST_3DDWithin(geometry g1, geometry g2, double precision distance_of_srid);

Description

For geometry type returns true if the 3d distance between two objects is within distance_of_srid specified projected units (spatialref units).



This method implements the SQL/MM specification. SQL-MM ?

Availability: 2.0.0

Examples



SELECT ST_3DDWithin(ST_Transform(ST_GeomFromEWKT(’SRID=4326;POINT(-72.1235 42.3521 4)’),2163),ST_Transform(ST_GeomFromEWKT(’SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 ←↩

20)’),2163),126.8

) As within_dist_3d,ST_DWithin(

ST_Transform(ST_GeomFromEWKT(’SRID=4326;POINT(-72.1235 42.3521 4)’),2163),ST_Transform(ST_GeomFromEWKT(’SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 ←↩

20)’),2163),126.8

) As within_dist_2d;

within_dist_3d | within_dist_2d----------------+----------------f | t

See Also

ST_3DDistance, ST_Distance, ST_DWithin, ST_3DMaxDistance, ST_Transform

8.8.4 ST_3DDFullyWithin

ST_3DDFullyWithin — Returns true if all of the 3D geometries are within the specified distance of one another.

Synopsis

boolean ST_3DDFullyWithin(geometry g1, geometry g2, double precision distance);


Description

Returns true if the 3D geometries are fully within the specified distance of one another. The distance is specified in units definedby the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of thesame coordinate projection, having the same SRID.

NoteThis function call will automatically include a bounding box comparison that will make use of any indexes that areavailable on the geometries.

Availability: 2.0.0



Examples

-- This compares the difference between fully within and distance within as well-- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully ←↩

withinSELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, ←↩

geom_b, 10) as D3DWithin10,ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from(select ST_GeomFromEWKT(’POINT(1 1 2)’) as geom_a,ST_GeomFromEWKT(’LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)’) as geom_b) t1;

d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20------------------+-------------+------------------+------------------f | t | t | f

See Also

ST_3DMaxDistance, ST_3DDWithin, ST_DWithin, ST_DFullyWithin

8.8.5 ST_3DIntersects

ST_3DIntersects — Returns TRUE if the Geometries "spatially intersect" in 3d - only for points and linestrings

Synopsis

boolean ST_3DIntersects( geometry geomA , geometry geomB );

Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries alsospatially intersect. Disjoint implies false for spatial intersection.

Availability: 2.0.0






Geometry Examples

SELECT ST_3DIntersects(pt, line), ST_Intersects(pt,line)FROM (SELECT ’POINT(0 0 2)’::geometry As pt,’LINESTRING (0 0 1, 0 2 3 )’::geometry As line) As foo;

st_3dintersects | st_intersects-----------------+---------------f | t

(1 row)

See Also

ST_Intersects

8.8.6 ST_3DLongestLine

ST_3DLongestLine — Returns the 3-dimensional longest line between two geometries

Synopsis

geometry ST_3DLongestLine(geometry g1, geometry g2);

Description

Returns the 3-dimensional longest line between two geometries. The function will only return the first longest line if more thanone. The line returned will always start in g1 and end in g2. The 3D length of the line this function returns will always be thesame as ST_3DMaxDistance returns for g1 and g2.

Availability: 2.0.0




Examples

linestring and point -- both 3d and 2d longest line

SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt



lol3d_line_pt | lol2d_line_pt-----------------------------------+----------------------------LINESTRING(50 75 1000,100 100 30) | LINESTRING(98 190,100 100)

linestring and multipoint -- both 3d and 2d longest line

SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt



lol3d_line_pt | lol2d_line_pt---------------------------------+--------------------------LINESTRING(98 190 1,50 74 1000) | LINESTRING(98 190,50 74)

Multilinestring and polygon both 3d and 2d longest line

SELECT ST_AsEWKT(ST_3DLongestLine(poly, mline)) As lol3d,ST_AsEWKT(ST_LongestLine(poly, mline)) As lol2d



(1 10 2, 5 20 1))’) As mline ) As foo;lol3d | lol2d

------------------------------+--------------------------LINESTRING(175 150 5,1 10 2) | LINESTRING(175 150,1 10)

See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_3DShortestLine, ST_3DMaxDistance

8.8.7 ST_3DMaxDistance

ST_3DMaxDistance — For geometry type Returns the 3-dimensional cartesian maximum distance (based on spatial ref) betweentwo geometries in projected units.

Synopsis

float ST_3DMaxDistance(geometry g1, geometry g2);


Description

For geometry type returns the 3-dimensional maximum cartesian distance between two geometries in projected units (spatial refunits).



Availability: 2.0.0

Examples



SELECT ST_3DMaxDistance(ST_Transform(ST_GeomFromEWKT(’SRID=4326;POINT(-72.1235 42.3521 10000)’),2163),ST_Transform(ST_GeomFromEWKT(’SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 ←↩

20)’),2163)) As dist_3d,ST_MaxDistance(

ST_Transform(ST_GeomFromEWKT(’SRID=4326;POINT(-72.1235 42.3521 10000)’),2163),ST_Transform(ST_GeomFromEWKT(’SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 ←↩

20)’),2163)) As dist_2d;

dist_3d | dist_2d------------------+------------------24383.7467488441 | 22247.8472107251

See Also

ST_Distance, ST_3DDWithin, ST_3DMaxDistance, ST_Transform

8.8.8 ST_3DShortestLine

ST_3DShortestLine — Returns the 3-dimensional shortest line between two geometries

Synopsis

geometry ST_3DShortestLine(geometry g1, geometry g2);

Description

Returns the 3-dimensional shortest line between two geometries. The function will only return the first shortest line if more thanone, that the function finds. If g1 and g2 intersects in just one point the function will return a line with both start and end in thatintersection-point. If g1 and g2 are intersecting with more than one point the function will return a line with start and end in thesame point but it can be any of the intersecting points. The line returned will always start in g1 and end in g2. The 3D length ofthe line this function returns will always be the same as ST_3DDistance returns for g1 and g2.

Availability: 2.0.0




Examples

linestring and point -- both 3d and 2d shortest line

SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt



shl3d_line_pt ←↩←↩

| shl2d_line_pt----------------------------------------------------------------------------+------------------------------------------------------ ←↩

LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30) | ←↩LINESTRING(73.0769230769231 115.384615384615,100 100)

linestring and multipoint -- both 3d and 2d shortest line

SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt



shl3d_line_pt | ←↩shl2d_line_pt

---------------------------------------------------------------------------+------------------------ ←↩

LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30) | LINESTRING ←↩(50 75,50 74)

Multilinestring and polygon both 3d and 2d shortest line

SELECT ST_AsEWKT(ST_3DShortestLine(poly, mline)) As shl3d,ST_AsEWKT(ST_ShortestLine(poly, mline)) As shl2d



(1 10 2, 5 20 1))’) As mline ) As foo;shl3d ←↩

| shl2d---------------------------------------------------------------------------------------------------+------------------------ ←↩

LINESTRING(39.993580415989 54.1889925532825 5,40.4078575708294 53.6052383805529 ←↩5.03423778139177) | LINESTRING(20 40,20 40)


See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_ShortestLine, ST_3DMaxDistance

8.8.9 ST_Area

ST_Area — Returns the area of the surface if it is a polygon or multi-polygon. For "geometry" type area is in SRID units. For"geography" area is in square meters.

Synopsis

float ST_Area(geometry g1);float ST_Area(geography geog, boolean use_spheroid=true);

Description

Returns the area of the geometry if it is a polygon or multi-polygon. Return the area measurement of an ST_Surface orST_MultiSurface value. For geometry Area is in the units of the srid. For geography area is in square meters and defaultsto measuring about the spheroid of the geography (currently only WGS84). To measure around the faster but less accurate sphere-- ST_Area(geog,false).

Enhanced: 2.0.0 - support for 2D polyhedral surfaces was introduced.




NoteFor polyhedral surfaces, only supports 2D polyhedral surfaces (not 2.5D). For 2.5D, may give a non-zero answer, butonly for the faces that sit completely in XY plane.

Examples

Return area in square feet for a plot of Massachusetts land and multiply by conversion to get square meters. Note this is in squarefeet because 2249 is Mass State Plane Feet

SELECT ST_Area(the_geom) As sqft, ST_Area(the_geom)*POWER(0.3048,2) As sqmFROM (SELECTST_GeomFromText(’POLYGON((743238 2967416,743238 2967450,

743265 2967450,743265.625 2967416,743238 2967416))’,2249) ) As foo(the_geom);sqft | sqm

---------+-------------928.625 | 86.27208552

Return area square feet and transform to Massachusetts state plane meters (26986) to get square meters. Note this is in squarefeet because 2249 is Mass State Plane Feet and transformed area is in square meters since 26986 is state plane mass meters



SELECT ST_Area(the_geom) As sqft, ST_Area(ST_Transform(the_geom,26986)) As sqmFROM (SELECTST_GeomFromText(’POLYGON((743238 2967416,743238 2967450,

743265 2967450,743265.625 2967416,743238 2967416))’,2249) ) As foo(the_geom);sqft | sqm

---------+------------------928.625 | 86.2724304199219

Return area square feet and square meters using Geography data type. Note that we transform to our geometry to geography(before you can do that make sure your geometry is in WGS 84 long lat 4326). Geography always measures in meters. This isjust for demonstration to compare. Normally your table will be stored in geography data type already.

SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft_spheroid, ST_Area(the_geog,false)/POWER ←↩(0.3048,2) As sqft_sphere, ST_Area(the_geog) As sqm_spheroidFROM (SELECTgeography(ST_Transform(

ST_GeomFromText(’POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 ←↩2967416,743238 2967416))’,

2249) ,4326

))

) As foo(the_geog);sqft_spheroid | sqft_sphere | sqm_spheroid

-----------------+------------------+------------------928.684405217197 | 927.186481558724 | 86.2776044452694

--if your data is in geography alreadySELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft, ST_Area(the_geog) As sqmFROM somegeogtable;

See Also

ST_GeomFromText, ST_GeographyFromText, ST_SetSRID, ST_Transform

8.8.10 ST_Azimuth

ST_Azimuth — Returns the angle in radians from the horizontal of the vector defined by pointA and pointB. Angle is computedclockwise from down-to-up: on the clock: 12=0; 3=PI/2; 6=PI; 9=3PI/2.

Synopsis

float ST_Azimuth(geometry pointA, geometry pointB);float ST_Azimuth(geography pointA, geography pointB);

Description

Returns the azimuth of the segment defined by the given Point geometries, or NULL if the two points are coincident. Returnvalue is in radians. Angle is computed clockwise from down-to-up: on the clock: 12=0; 3=PI/2; 6=PI; 9=3PI/2

The Azimuth is mathematical concept defined as the angle, in this case measured in radian, between a reference plane and apoint.


Availability: 1.1.0

Enhanced: 2.0.0 support for geography was introduced.

Azimuth is especially useful in conjunction with ST_Translate for shifting an object along its perpendicular axis. See up-gis_lineshift Plpgsqlfunctions PostGIS wiki section for example of this.

Examples

Geometry Azimuth in degrees

SELECT ST_Azimuth(ST_Point(25,45), ST_Point(75,100))/(2*pi())*360 as degAz,ST_Azimuth(ST_Point(75,100), ST_Point(25,45))/(2*pi())*360 As degAzrev;

-- NOTE easier to remember syntax using PostgreSQL built-in degrees function ---- Both yield same answer --SELECT degrees( ST_Azimuth(ST_Point(25,45), ST_Point(75,100)) ) as degAz,

degrees( ST_Azimuth(ST_Point(75,100), ST_Point(25,45)) ) As degAzrev;

degaz | degazrev------------------+------------------42.2736890060937 | 222.273689006094

degAz is path to travel (azimuth), horizontal line (whichstarts at the start point and ends where we want the endpoint to fall) and points (start point: 25,45 is in green)

degAzrev is azimuth curve shown, horizontal line (whichstarts at the start point and ends where we want the endpoint to fall) and points (start point: 75,100 is in green)

See Also

ST_Point, ST_Translate

8.8.11 ST_Centroid

ST_Centroid — Returns the geometric center of a geometry.

http://trac.osgeo.org/postgis/wiki/UsersWikiplpgsqlfunctions


Synopsis

geometry ST_Centroid(geometry g1);

Description

Computes the geometric center of a geometry, or equivalently, the center of mass of the geometry as a POINT. For [MULTI]P-OINTs, this is computed as the arithmetric mean of the input coordinates. For [MULTI]LINESTRINGs, this is computed as theweighted length of each line segment. For [MULTI]POLYGONs, "weight" is thought in terms of area. If an empty geometry issupplied, an empty GEOMETRYCOLLECTION is returned. If NULL is supplied, NULL is returned.

The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimensiongeometries contribute zero "weight" to the centroid).

NoteComputation will be more accurate if performed by the GEOS module (enabled at compile time).



Examples

In each of the following illustrations, the blue dot represents the centroid of the source geometry.

Centroid of a MULTIPOINT Centroid of a LINESTRING



Centroid of a POLYGON Centroid of a GEOMETRYCOLLECTION

SELECT ST_AsText(ST_Centroid(’MULTIPOINT ( -1 0, -1 2, -1 3, -1 4, -1 7, 0 1, 0 3, 1 1, 2 ←↩0, 6 0, 7 8, 9 8, 10 6 )’));

st_astext------------------------------------------POINT(2.30769230769231 3.30769230769231)

(1 row)

See Also

ST_PointOnSurface

8.8.12 ST_ClosestPoint

ST_ClosestPoint — Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of the shortest line.

Synopsis

geometry ST_ClosestPoint(geometry g1, geometry g2);

Description

Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of the shortest line.

NoteIf you have a 3D Geometry, you may prefer to use ST_3DClosestPoint.

Availability: 1.5.0

Examples


Closest between point and linestring is the point itself, butclosest point between a linestring and point is the point on

line string that is closest.

SELECT ST_AsText(ST_ClosestPoint(pt,line) ←↩) AS cp_pt_line,

ST_AsText(ST_ClosestPoint(line,pt ←↩)) As cp_line_pt

FROM (SELECT ’POINT(100 100)’::geometry ←↩As pt,

’LINESTRING (20 80, 98 ←↩190, 110 180, 50 75 )’::geometry As line

) As foo;

cp_pt_line | ←↩cp_line_pt

----------------+------------------------------------------ ←↩

POINT(100 100) | POINT(73.0769230769231 ←↩115.384615384615)

closest point on polygon A to polygon B

SELECT ST_AsText(ST_ClosestPoint(

ST_GeomFromText(’ ←↩POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))’),

ST_Buffer( ←↩ST_GeomFromText(’POINT(110 170)’), 20)

)) As ptwkt;

ptwkt------------------------------------------ ←↩

POINT(140.752120669087 125.695053378061)

See Also

ST_3DClosestPoint,ST_Distance, ST_LongestLine, ST_ShortestLine, ST_MaxDistance

8.8.13 ST_Contains

ST_Contains — Returns true if and only if no points of B lie in the exterior of A, and at least one point of the interior of B liesin the interior of A.

Synopsis

boolean ST_Contains(geometry geomA, geometry geomB);


Description

Geometry A contains Geometry B if and only if no points of B lie in the exterior of A, and at least one point of the interior of Blies in the interior of A. An important subtlety of this definition is that A does not contain its boundary, but A does contain itself.Contrast that to ST_ContainsProperly where geometry A does not Contain Properly itself.

Returns TRUE if geometry B is completely inside geometry A. For this function to make sense, the source geometries must bothbe of the same coordinate projection, having the same SRID. ST_Contains is the inverse of ST_Within. So ST_Contains(A,B)implies ST_Within(B,A) except in the case of invalid geometries where the result is always false regardless or not defined.


ImportantDo not call with a GEOMETRYCOLLECTION as an argument

ImportantDo not use this function with invalid geometries. You will get unexpected results.

This function call will automatically include a bounding box comparison that will make use of any indexes that are available onthe geometries. To avoid index use, use the function _ST_Contains.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 -same as within(geometry B, geometry A)


There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious. For details check out Subtleties ofOGC Covers, Contains, Within

Examples

The ST_Contains predicate returns TRUE in all the following illustrations.


http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html



LINESTRING / MULTIPOINT POLYGON / POINT

POLYGON / LINESTRING POLYGON / POLYGON

The ST_Contains predicate returns FALSE in all the following illustrations.


POLYGON / MULTIPOINT POLYGON / LINESTRING

-- A circle within a circleSELECT ST_Contains(smallc, bigc) As smallcontainsbig,

ST_Contains(bigc,smallc) As bigcontainssmall,ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior

FROM (SELECT ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 10) As smallc,ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 20) As bigc) As foo;

-- Resultsmallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | ←↩

bigcontainsexterior------------------+------------------+------------------+------------+-------------------+--------------------- ←↩

f | t | t | t | t | f

-- Example demonstrating difference between contains and contains properlySELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ←↩

ST_ContainsProperly(geomA, geomA) AS acontainspropa,ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ←↩

ST_Boundary(geomA)) As acontainspropbaFROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),

( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),( ST_Point(1,1) )

) As foo(geomA);

geomtype | acontainsa | acontainspropa | acontainsba | acontainspropba--------------+------------+----------------+-------------+-----------------ST_Polygon | t | f | f | fST_LineString | t | f | f | fST_Point | t | t | f | f


See Also

ST_Boundary, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Equals, ST_Within

8.8.14 ST_ContainsProperly

ST_ContainsProperly — Returns true if B intersects the interior of A but not the boundary (or exterior). A does not containproperly itself, but does contain itself.

Synopsis

boolean ST_ContainsProperly(geometry geomA, geometry geomB);

Description

Returns true if B intersects the interior of A but not the boundary (or exterior).

A does not contain properly itself, but does contain itself.

Every point of the other geometry is a point of this geometry’s interior. The DE-9IM Intersection Matrix for the two geometriesmatches [T**FF*FF*] used in ST_Relate

NoteFrom JTS docs slightly reworded: The advantage to using this predicate over ST_Contains and ST_Intersects is that itcan be computed efficiently, with no need to compute topology at individual points.An example use case for this predicate is computing the intersections of a set of geometries with a large polygonalgeometry. Since intersection is a fairly slow operation, it can be more efficient to use containsProperly to filter out testgeometries which lie wholly inside the area. In these cases the intersection is known a priori to be exactly the originaltest geometry.




This function call will automatically include a bounding box comparison that will make use of any indexes that are available onthe geometries. To avoid index use, use the function _ST_ContainsProperly.

Examples


--a circle within a circleSELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,ST_ContainsProperly(bigc, ST_ExteriorRing(bigc)) As bigcontainsexteriorFROM (SELECT ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 10) As smallc,ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 20) As bigc) As foo;--Resultsmallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | ←↩

bigcoversexterior | bigcontainsexterior------------------+------------------+------------------+------------+-------------------+--------------------- ←↩

f | t | f | t | t ←↩| f

--example demonstrating difference between contains and contains properlySELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ←↩

ST_ContainsProperly(geomA, geomA) AS acontainspropa,ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ←↩

ST_Boundary(geomA)) As acontainspropbaFROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),

( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),( ST_Point(1,1) )

) As foo(geomA);

geomtype | acontainsa | acontainspropa | acontainsba | acontainspropba--------------+------------+----------------+-------------+-----------------ST_Polygon | t | f | f | fST_LineString | t | f | f | fST_Point | t | t | f | f

See Also

ST_GeometryType, ST_Boundary, ST_Contains, ST_Covers, ST_CoveredBy, ST_Equals, ST_Relate, ST_Within

8.8.15 ST_Covers

ST_Covers — Returns 1 (TRUE) if no point in Geometry B is outside Geometry A

Synopsis

boolean ST_Covers(geometry geomA, geometry geomB);boolean ST_Covers(geography geogpolyA, geography geogpointB);

Description

Returns 1 (TRUE) if no point in Geometry/Geography B is outside Geometry/Geography A




ImportantFor geography only Polygon covers point is supported.


This function call will automatically include a bounding box comparison that will make use of any indexes that are available onthe geometries. To avoid index use, use the function _ST_Covers.

Availability: 1.2.2 - requires GEOS >= 3.0

Availability: 1.5 - support for geography was introduced.


Not an OGC standard, but Oracle has it too.


Examples

Geometry example

--a circle covering a circleSELECT ST_Covers(smallc,smallc) As smallinsmall,

ST_Covers(smallc, bigc) As smallcoversbig,ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior

FROM (SELECT ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 10) As smallc,ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 20) As bigc) As foo;--Result

smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior--------------+----------------+-------------------+---------------------t | f | t | f

(1 row)

Geeography Example

-- a point with a 300 meter buffer compared to a point, a point and its 10 meter bufferSELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt,

ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_centFROM (SELECT ST_Buffer(ST_GeogFromText(’SRID=4326;POINT(-99.327 31.4821)’), 300) As ←↩

geog_poly,ST_GeogFromText(’SRID=4326;POINT(-99.33 31.483)’) As geog_pt ) As foo;

poly_covers_pt | buff_10m_covers_cent----------------+------------------f | t

See Also

ST_Contains, ST_CoveredBy, ST_Within




8.8.16 ST_CoveredBy

ST_CoveredBy — Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B

Synopsis

boolean ST_CoveredBy(geometry geomA, geometry geomB);boolean ST_CoveredBy(geography geogA, geography geogB);

Description

Returns 1 (TRUE) if no point in Geometry/Geography A is outside Geometry/Geography B




Availability: 1.2.2 - requires GEOS >= 3.0

This function call will automatically include a bounding box comparison that will make use of any indexes that are available onthe geometries. To avoid index use, use the function _ST_CoveredBy.


Not an OGC standard, but Oracle has it too.


Examples

--a circle coveredby a circleSELECT ST_CoveredBy(smallc,smallc) As smallinsmall,

ST_CoveredBy(smallc, bigc) As smallcoveredbybig,ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig

FROM (SELECT ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 10) As smallc,ST_Buffer(ST_GeomFromText(’POINT(1 2)’), 20) As bigc) As foo;--Result

smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig--------------+-------------------+----------------------+------------------t | t | t | f

(1 row)

See Also

ST_Contains, ST_Covers, ST_ExteriorRing, ST_Within




8.8.17 ST_Crosses

ST_Crosses — Returns TRUE if the supplied geometries have some, but not all, interior points in common.

Synopsis

boolean ST_Crosses(geometry g1, geometry g2);

Description

ST_Crosses takes two geometry objects and returns TRUE if their intersection "spatially cross", that is, the geometries havesome, but not all interior points in common. The intersection of the interiors of the geometries must not be the empty set andmust have a dimensionality less than the the maximum dimension of the two input geometries. Additionally, the intersection ofthe two geometries must not equal either of the source geometries. Otherwise, it returns FALSE.

In mathematical terms, this is expressed as:

The DE-9IM Intersection Matrix for the two geometries is:

• T*T****** (for Point/Line, Point/Area, and Line/Area situations)

• T*****T** (for Line/Point, Area/Point, and Area/Line situations)

• 0******** (for Line/Line situations)

For any other combination of dimensions this predicate returns false.

The OpenGIS Simple Features Specification defines this predicate only for Point/Line, Point/Area, Line/Line, and Line/Areasituations. JTS / GEOS extends the definition to apply to Line/Point, Area/Point and Area/Line situations as well. This makesthe relation symmetric.





TODO: Insert appropriate MathML markup here or use a gif. Simple HTML markup does not work well in both IE and Firefox.



Examples

The following illustrations all return TRUE.

MULTIPOINT / LINESTRING MULTIPOINT / POLYGON

LINESTRING / POLYGON LINESTRING / LINESTRING

Consider a situation where a user has two tables: a table of roads and a table of highways.


CREATE TABLE roads (id serial NOT NULL,the_geom geometry,CONSTRAINT roads_pkey PRIMARY KEY ( ←↩road_id)

);

CREATE TABLE highways (id serial NOT NULL,the_gem geometry,CONSTRAINT roads_pkey PRIMARY KEY ( ←↩road_id)

);

To determine a list of roads that cross a highway, use a query similiar to:

SELECT roads.idFROM roads, highwaysWHERE ST_Crosses(roads.the_geom, highways.the_geom);

8.8.18 ST_LineCrossingDirection

ST_LineCrossingDirection — Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior.0 is no crossing.

Synopsis

integer ST_LineCrossingDirection(geometry linestringA, geometry linestringB);

Description

Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing. This is onlysupported for LINESTRING

Definition of integer constants is as follows:

• 0: LINE NO CROSS

• -1: LINE CROSS LEFT

• 1: LINE CROSS RIGHT

• -2: LINE MULTICROSS END LEFT

• 2: LINE MULTICROSS END RIGHT

• -3: LINE MULTICROSS END SAME FIRST LEFT

• 3: LINE MULTICROSS END SAME FIRST RIGHT

Availability: 1.4

Examples


Line 1 (green), Line 2 ball is start point, triangle are endpoints. Query below.

SELECT ST_LineCrossingDirection(foo.line1 ←↩, foo.line2) As l1_cross_l2 ,

ST_LineCrossingDirection(foo. ←↩line2, foo.line1) As l2_cross_l1

FROM (SELECTST_GeomFromText(’LINESTRING(25 169,89 ←↩

114,40 70,86 43)’) As line1,ST_GeomFromText(’LINESTRING(171 154,20 ←↩

140,71 74,161 53)’) As line2) As foo;

l1_cross_l2 | l2_cross_l1-------------+-------------

3 | -3

Line 1 (green), Line 2 (blue) ball is start point, triangle areend points. Query below.



FROM (SELECTST_GeomFromText(’LINESTRING(25 169,89 ←↩114,40 70,86 43)’) As line1,

ST_GeomFromText(’LINESTRING (171 154, ←↩20 140, 71 74, 2.99 90.16)’) As line2

) As foo;

l1_cross_l2 | l2_cross_l1-------------+-------------

2 | -2



SELECTST_LineCrossingDirection(foo. ←↩

line1, foo.line2) As l1_cross_l2 ,ST_LineCrossingDirection(foo. ←↩

line2, foo.line1) As l2_cross_l1FROM (SELECTST_GeomFromText(’LINESTRING(25 169,89 ←↩114,40 70,86 43)’) As line1,

ST_GeomFromText(’LINESTRING (20 140, 71 ←↩74, 161 53)’) As line2

) As foo;

l1_cross_l2 | l2_cross_l1-------------+-------------

-1 | 1




FROM (SELECTST_GeomFromText(’LINESTRING(25 ←↩

169,89 114,40 70,86 43)’) As line1,ST_GeomFromText(’LINESTRING(2.99 ←↩

90.16,71 74,20 140,171 154)’) As line2) As foo;

l1_cross_l2 | l2_cross_l1-------------+-------------

-2 | 2

SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.the_geom, s2.the_geom)FROM streets s1 CROSS JOIN streets s2 ON (s1.gid != s2.gid AND s1.the_geom && s2.the_geom ←↩

)WHERE ST_CrossingDirection(s1.the_geom, s2.the_geom) > 0;

See Also

ST_Crosses

8.8.19 ST_Disjoint

ST_Disjoint — Returns TRUE if the Geometries do not "spatially intersect" - if they do not share any space together.


Synopsis

boolean ST_Disjoint( geometry A , geometry B );

Description

Overlaps, Touches, Within all imply geometries are not spatially disjoint. If any of the aforementioned returns true, then thegeometries are not spatially disjoint. Disjoint implies false for spatial intersection.



NoteThis function call does not use indexes

NoteNOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 -a.Relate(b, ’FF*FF****’)


Examples

SELECT ST_Disjoint(’POINT(0 0)’::geometry, ’LINESTRING ( 2 0, 0 2 )’::geometry);st_disjoint

---------------t

(1 row)SELECT ST_Disjoint(’POINT(0 0)’::geometry, ’LINESTRING ( 0 0, 0 2 )’::geometry);st_disjoint

---------------f

(1 row)

See Also

ST_IntersectsST_Intersects



8.8.20 ST_Distance

ST_Distance — For geometry type Returns the 2-dimensional cartesian minimum distance (based on spatial ref) between twogeometries in projected units. For geography type defaults to return spheroidal minimum distance between two geographies inmeters.

Synopsis

float ST_Distance(geometry g1, geometry g2);float ST_Distance(geography gg1, geography gg2);float ST_Distance(geography gg1, geography gg2, boolean use_spheroid);

Description

For geometry type returns the 2-dimensional minimum cartesian distance between two geometries in projected units (spatial refunits). For geography type defaults to return the minimum distance around WGS 84 spheroid between two geographies in meters.Pass in false to return answer in sphere instead of spheroid.



Availability: 1.5.0 geography support was introduced in 1.5. Speed improvements for planar to better handle large or many vertexgeometries

Examples

--Geometry example - units in planar degrees 4326 is WGS 84 long lat unit=degreesSELECT ST_Distance(

ST_GeomFromText(’POINT(-72.1235 42.3521)’,4326),ST_GeomFromText(’LINESTRING(-72.1260 42.45, -72.123 42.1546)’, 4326)

);st_distance-----------------0.00150567726382282

-- Geometry example - units in meters (SRID: 26986 Massachusetts state plane meters) (most ←↩accurate for Massachusetts)

SELECT ST_Distance(ST_Transform(ST_GeomFromText(’POINT(-72.1235 42.3521)’,4326),26986),ST_Transform(ST_GeomFromText(’LINESTRING(-72.1260 42.45, -72.123 42.1546)’, 4326) ←↩

,26986));

st_distance-----------------123.797937878454

-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (least ←↩accurate)

SELECT ST_Distance(ST_Transform(ST_GeomFromText(’POINT(-72.1235 42.3521)’,4326),2163),ST_Transform(ST_GeomFromText(’LINESTRING(-72.1260 42.45, -72.123 42.1546)’, 4326) ←↩

,2163));

st_distance------------------



126.664256056812

-- Geography example -- same but note units in meters - use sphere for slightly faster less ←↩accurate

SELECT ST_Distance(gg1, gg2) As spheroid_dist, ST_Distance(gg1, gg2, false) As sphere_distFROM (SELECT

ST_GeographyFromText(’SRID=4326;POINT(-72.1235 42.3521)’) As gg1,ST_GeographyFromText(’SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)’) As gg2) As foo ;

spheroid_dist | sphere_dist------------------+------------------123.802076746848 | 123.475736916397

See Also

ST_3DDistance, ST_DWithin, ST_Distance_Sphere, ST_Distance_Spheroid, ST_MaxDistance, ST_Transform

8.8.21 ST_HausdorffDistance

ST_HausdorffDistance — Returns the Hausdorff distance between two geometries. Basically a measure of how similar ordissimilar 2 geometries are. Units are in the units of the spatial reference system of the geometries.

Synopsis

float ST_HausdorffDistance(geometry g1, geometry g2);float ST_HausdorffDistance(geometry g1, geometry g2, float densifyFrac);

Description

Implements algorithm for computing a distance metric which can be thought of as the "Discrete Hausdorff Distance". This is theHausdorff distance restricted to discrete points for one of the geometries. Wikipedia article on Hausdorff distance Martin Davisnote on how Hausdorff Distance calculation was used to prove correctness of the CascadePolygonUnion approach.

When densifyFrac is specified, this function performs a segment densification before computing the discrete hausdorff distance.The densifyFrac parameter sets the fraction by which to densify each segment. Each segment will be split into a number ofequal-length subsegments, whose fraction of the total length is closest to the given fraction.

NoteThe current implementation supports only vertices as the discrete locations. This could be extended to allow an arbitrarydensity of points to be used.

NoteThis algorithm is NOT equivalent to the standard Hausdorff distance. However, it computes an approximation that iscorrect for a large subset of useful cases. One important part of this subset is Linestrings that are roughly parallel toeach other, and roughly equal in length. This is a useful metric for line matching.

Availability: 1.5.0 - requires GEOS >= 3.2.0

http://en.wikipedia.org/wiki/Hausdorff_distance

http://lin-ear-th-inking.blogspot.com/2009/01/computing-geometric-similarity.html

http://lin-ear-th-inking.blogspot.com/2009/01/computing-geometric-similarity.html


Examples

postgis=# SELECT st_HausdorffDistance(’LINESTRING (0 0, 2 0)’::geometry,’MULTIPOINT (0 1, 1 0, 2 1)’::geometry);

st_hausdorffdistance----------------------

1(1 row)

postgis=# SELECT st_hausdorffdistance(’LINESTRING (130 0, 0 0, 0 150)’::geometry, ’ ←↩LINESTRING (10 10, 10 150, 130 10)’::geometry, 0.5);

st_hausdorffdistance----------------------

70(1 row)

8.8.22 ST_MaxDistance

ST_MaxDistance — Returns the 2-dimensional largest distance between two geometries in projected units.

Synopsis

float ST_MaxDistance(geometry g1, geometry g2);

Description

Some useful description here.

NoteReturns the 2-dimensional maximum distance between two linestrings in projected units. If g1 and g2 is the samegeometry the function will return the distance between the two vertices most far from each other in that geometry.

Availability: 1.5.0

Examples

postgis=# SELECT ST_MaxDistance(’POINT(0 0)’::geometry, ’LINESTRING ( 2 0, 0 2 )’::geometry ←↩);st_maxdistance

-----------------2

(1 row)

postgis=# SELECT ST_MaxDistance(’POINT(0 0)’::geometry, ’LINESTRING ( 2 2, 2 2 )’::geometry ←↩);

st_maxdistance------------------2.82842712474619

(1 row)


See Also

ST_Distance, ST_LongestLine

8.8.23 ST_Distance_Sphere

ST_Distance_Sphere — Returns minimum distance in meters between two lon/lat geometries. Uses a spherical earth and radiusof 6370986 meters. Faster than ST_Distance_Spheroid ST_Distance_Spheroid, but less accurate. PostGIS versions prior to 1.5only implemented for points.

Synopsis

float ST_Distance_Sphere(geometry geomlonlatA, geometry geomlonlatB);

Description

Returns minimum distance in meters between two lon/lat points. Uses a spherical earth and radius of 6370986 meters. Fasterthan ST_Distance_Spheroid, but less accurate. PostGIS Versions prior to 1.5 only implemented for points.

NoteThis function currently does not look at the SRID of a geometry and will always assume its in WGS 84 long lat. Priorversions of this function only support points.

Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.

Examples

SELECT round(CAST(ST_Distance_Sphere(ST_Centroid(the_geom), ST_GeomFromText(’POINT(-118 38) ←↩’,4326)) As numeric),2) As dist_meters,

round(CAST(ST_Distance(ST_Transform(ST_Centroid(the_geom),32611),ST_Transform(ST_GeomFromText(’POINT(-118 38)’, 4326),32611)) As numeric),2) As ←↩

dist_utm11_meters,round(CAST(ST_Distance(ST_Centroid(the_geom), ST_GeomFromText(’POINT(-118 38)’, 4326)) As ←↩

numeric),5) As dist_degrees,round(CAST(ST_Distance(ST_Transform(the_geom,32611),

ST_Transform(ST_GeomFromText(’POINT(-118 38)’, 4326),32611)) As numeric),2) As ←↩min_dist_line_point_meters

FROM(SELECT ST_GeomFromText(’LINESTRING(-118.584 38.374,-118.583 38.5)’, 4326) As the_geom) ←↩

as foo;dist_meters | dist_utm11_meters | dist_degrees | min_dist_line_point_meters

-------------+-------------------+--------------+----------------------------70424.47 | 70438.00 | 0.72900 | 65871.18

See Also

ST_Distance, ST_Distance_Spheroid

8.8.24 ST_Distance_Spheroid

ST_Distance_Spheroid — Returns the minimum distance between two lon/lat geometries given a particular spheroid. PostGISversions prior to 1.5 only support points.


Synopsis

float ST_Distance_Spheroid(geometry geomlonlatA, geometry geomlonlatB, spheroid measurement_spheroid);

Description

Returns minimum distance in meters between two lon/lat geometries given a particular spheroid. See the explanation of spheroidsgiven for ST_Length_Spheroid. PostGIS version prior to 1.5 only support points.

NoteThis function currently does not look at the SRID of a geometry and will always assume its represented in the coordi-nates of the passed in spheroid. Prior versions of this function only support points.

Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.

Examples

SELECT round(CAST(ST_Distance_Spheroid(ST_Centroid(the_geom), ST_GeomFromText(’POINT(-118 38)’,4326), ’ ←↩

SPHEROID["WGS 84",6378137,298.257223563]’)As numeric),2) As dist_meters_spheroid,

round(CAST(ST_Distance_Sphere(ST_Centroid(the_geom), ST_GeomFromText(’POINT(-118 38) ←↩’,4326)) As numeric),2) As dist_meters_sphere,

round(CAST(ST_Distance(ST_Transform(ST_Centroid(the_geom),32611),ST_Transform(ST_GeomFromText(’POINT(-118 38)’, 4326),32611)) As numeric),2) As ←↩

dist_utm11_metersFROM

(SELECT ST_GeomFromText(’LINESTRING(-118.584 38.374,-118.583 38.5)’, 4326) As the_geom) ←↩as foo;

dist_meters_spheroid | dist_meters_sphere | dist_utm11_meters----------------------+--------------------+-------------------

70454.92 | 70424.47 | 70438.00

See Also

ST_Distance, ST_Distance_Sphere

8.8.25 ST_DFullyWithin

ST_DFullyWithin — Returns true if all of the geometries are within the specified distance of one another

Synopsis

boolean ST_DFullyWithin(geometry g1, geometry g2, double precision distance);


Description

Returns true if the geometries is fully within the specified distance of one another. The distance is specified in units defined bythe spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the samecoordinate projection, having the same SRID.


Availability: 1.5.0

Examples

postgis=# SELECT ST_DFullyWithin(geom_a, geom_b, 10) as DFullyWithin10, ST_DWithin(geom_a, ←↩geom_b, 10) as DWithin10, ST_DFullyWithin(geom_a, geom_b, 20) as DFullyWithin20 from(select ST_GeomFromText(’POINT(1 1)’) as geom_a,ST_GeomFromText(’LINESTRING(1 5, 2 7, 1 ←↩

9, 14 12)’) as geom_b) t1;

-----------------DFullyWithin10 | DWithin10 | DFullyWithin20 |

---------------+----------+---------------+f | t | t |

See Also

ST_MaxDistance, ST_DWithin

8.8.26 ST_DWithin

ST_DWithin — Returns true if the geometries are within the specified distance of one another. For geometry units are in thoseof spatial reference and For geography units are in meters and measurement is defaulted to use_spheroid=true (measure aroundspheroid), for faster check, use_spheroid=false to measure along sphere.

Synopsis

boolean ST_DWithin(geometry g1, geometry g2, double precision distance_of_srid);boolean ST_DWithin(geography gg1, geography gg2, double precision distance_meters);boolean ST_DWithin(geography gg1, geography gg2, double precision distance_meters, boolean use_spheroid);

Description

Returns true if the geometries are within the specified distance of one another.

For Geometries: The distance is specified in units defined by the spatial reference system of the geometries. For this function tomake sense, the source geometries must both be of the same coordinate projection, having the same SRID.

For geography units are in meters and measurement is defaulted to use_spheroid=true (measure around WGS 84 spheroid), forfaster check, use_spheroid=false to measure along sphere.



NotePrior to 1.3, ST_Expand was commonly used in conjunction with && and ST_Distance to achieve the same effect andin pre-1.3.4 this function was basically short-hand for that construct. From 1.3.4, ST_DWithin uses a more short-circuitdistance function which should make it more efficient than prior versions for larger buffer regions.

NoteUse ST_3DDWithin if you have 3D geometries.


Availability: 1.5.0 support for geography was introduced

Examples

--Find the nearest hospital to each school--that is within 3000 units of the school.-- We do an ST_DWithin search to utilize indexes to limit our search list-- that the non-indexable ST_Distance needs to process--If the units of the spatial reference is meters then units would be metersSELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.the_geom, h.hospital_name

FROM schools sLEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)

ORDER BY s.gid, ST_Distance(s.the_geom, h.the_geom);

--The schools with no close hospitals--Find all schools with no hospital within 3000 units--away from the school. Units is in units of spatial ref (e.g. meters, feet, degrees)SELECT s.gid, s.school_name

FROM schools sLEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)

WHERE h.gid IS NULL;

See Also

ST_Distance, ST_Expand

8.8.27 ST_Equals

ST_Equals — Returns true if the given geometries represent the same geometry. Directionality is ignored.

Synopsis

boolean ST_Equals(geometry A, geometry B);



Description

Returns TRUE if the given Geometries are "spatially equal". Use this for a ’better’ answer than ’=’. Note by spatially equal wemean ST_Within(A,B) = true and ST_Within(B,A) = true and also mean ordering of points can be different but represent the samegeometry structure. To verify the order of points is consistent, use ST_OrderingEquals (it must be noted ST_OrderingEquals isa little more stringent than simply verifying order of points are the same).

ImportantThis function will return false if either geometry is invalid even if they are binary equal.



Examples

SELECT ST_Equals(ST_GeomFromText(’LINESTRING(0 0, 10 10)’),ST_GeomFromText(’LINESTRING(0 0, 5 5, 10 10)’));

st_equals-----------t

(1 row)

SELECT ST_Equals(ST_Reverse(ST_GeomFromText(’LINESTRING(0 0, 10 10)’)),ST_GeomFromText(’LINESTRING(0 0, 5 5, 10 10)’));

st_equals-----------t

(1 row)

See Also

ST_IsValid, ST_OrderingEquals, ST_Reverse, ST_Within

8.8.28 ST_HasArc

ST_HasArc — Returns true if a geometry or geometry collection contains a circular string

Synopsis

boolean ST_HasArc(geometry geomA);

Description

Returns true if a geometry or geometry collection contains a circular string

Availability: 1.2.3?





Examples

SELECT ST_HasArc(ST_Collect(’LINESTRING(1 2, 3 4, 5 6)’, ’CIRCULARSTRING(1 1, 2 3, 4 5, 6 ←↩7, 5 6)’));st_hasarc--------t

See Also

ST_CurveToLine, ST_LineToCurve

8.8.29 ST_Intersects

ST_Intersects — Returns TRUE if the Geometries/Geography "spatially intersect in 2D" - (share any portion of space) andFALSE if they don’t (they are Disjoint). For geography -- tolerance is 0.00001 meters (so any points that close are considered tointersect)

Synopsis

boolean ST_Intersects( geometry geomA , geometry geomB );boolean ST_Intersects( geography geogA , geography geogB );

Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries alsospatially intersect. Disjoint implies false for spatial intersection.

ImportantDo not call with a GEOMETRYCOLLECTION as an argument for geometry version. The geography version supportsGEOMETRYCOLLECTION since its a thin wrapper around distance implementation.

Performed by the GEOS module (for geometry), geography is native

Availability: 1.5 support for geography was introduced.


NoteFor geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather than spheroidcalculation.

NoteNOTE: this is the "allowable" version that returns a boolean, not an integer.


This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 -ST_Intersects(g1, g2 ) --> Not (ST_Disjoint(g1, g2 ))


Geometry Examples

SELECT ST_Intersects(’POINT(0 0)’::geometry, ’LINESTRING ( 2 0, 0 2 )’::geometry);st_intersects

---------------f

(1 row)SELECT ST_Intersects(’POINT(0 0)’::geometry, ’LINESTRING ( 0 0, 0 2 )’::geometry);st_intersects

---------------t

(1 row)

Geography Examples

SELECT ST_Intersects(ST_GeographyFromText(’SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)’),ST_GeographyFromText(’SRID=4326;POINT(-43.23456 72.4567772)’));

st_intersects---------------t

See Also

ST_3DIntersects, ST_Disjoint

8.8.30 ST_Length

ST_Length — Returns the 2d length of the geometry if it is a linestring or multilinestring. geometry are in units of spatialreference and geography are in meters (default spheroid)

Synopsis

float ST_Length(geometry a_2dlinestring);float ST_Length(geography geog, boolean use_spheroid=true);

Description

For geometry: Returns the cartesian 2D length of the geometry if it is a linestring, multilinestring, ST_Curve, ST_MultiCurve. 0is returned for areal geometries. For areal geometries use ST_Perimeter. Geometry: Measurements are in the units of the spatialreference system of the geometry. Geography: Units are in meters and also acts as a Perimeter function for areal geogs.

Currently for geometry this is an alias for ST_Length2D, but this may change to support higher dimensions.



WarningChanged: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would giveyou the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0 this was changed to return 0 to be in line with geometrybehavior. Please use ST_Perimeter if you want the perimeter of a polygon

NoteFor geography measurement defaults spheroid measurement. To use the faster less accurate sphere useST_Length(gg,false);



Availability: 1.5.0 geography support was introduced in 1.5.

Geometry Examples

Return length in feet for line string. Note this is in feet because 2249 is Mass State Plane Feet

SELECT ST_Length(ST_GeomFromText(’LINESTRING(743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416)’,2249));st_length---------122.630744000095

--Transforming WGS 84 linestring to Massachusetts state plane metersSELECT ST_Length(

ST_Transform(ST_GeomFromEWKT(’SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 ←↩

42.1546)’),26986

));st_length---------34309.4563576191

Geography Examples

Return length of WGS 84 geography line

-- default calculation is using a sphere rather than spheroidSELECT ST_Length(the_geog) As length_spheroid, ST_Length(the_geog,false) As length_sphereFROM (SELECT ST_GeographyFromText(’SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)’) As the_geog)As foo;length_spheroid | length_sphere

------------------+------------------34310.5703627305 | 34346.2060960742

(1 row)



See Also

ST_GeographyFromText, ST_GeomFromEWKT, ST_Length_Spheroid, ST_Perimeter, ST_Transform

8.8.31 ST_Length2D

ST_Length2D — Returns the 2-dimensional length of the geometry if it is a linestring or multi-linestring. This is an alias forST_Length

Synopsis

float ST_Length2D(geometry a_2dlinestring);

Description

Returns the 2-dimensional length of the geometry if it is a linestring or multi-linestring. This is an alias for ST_Length

See Also

ST_Length, ST_3DLength

8.8.32 ST_3DLength

ST_3DLength — Returns the 3-dimensional or 2-dimensional length of the geometry if it is a linestring or multi-linestring.

Synopsis

float ST_3DLength(geometry a_3dlinestring);

Description

Returns the 3-dimensional or 2-dimensional length of the geometry if it is a linestring or multi-linestring. For 2-d lines it willjust return the 2-d length (same as ST_Length and ST_Length2D)


Changed: 2.0.0 In prior versions this used to be called ST_Length3D

Examples

Return length in feet for a 3D cable. Note this is in feet because 2249 is Mass State Plane Feet

SELECT ST_3DLength(ST_GeomFromText(’LINESTRING(743238 2967416 1,743238 2967450 1,743265 ←↩2967450 3,

743265.625 2967416 3,743238 2967416 3)’,2249));ST_3DLength-----------122.704716741457

See Also

ST_Length, ST_Length2D


8.8.33 ST_Length_Spheroid

ST_Length_Spheroid — Calculates the 2D or 3D length of a linestring/multilinestring on an ellipsoid. This is useful if thecoordinates of the geometry are in longitude/latitude and a length is desired without reprojection.

Synopsis

float ST_Length_Spheroid(geometry a_linestring, spheroid a_spheroid);

Description

Calculates the length of a geometry on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude anda length is desired without reprojection. The ellipsoid is a separate database type and can be constructed as follows:

SPHEROID[<NAME>,<SEMI-MAJORAXIS>,<INVERSE FLATTENING>]

SPHEROID["GRS_1980",6378137,298.257222101]

NoteWill return 0 for anything that is not a MULTILINESTRING or LINESTRING


Examples

SELECT ST_Length_Spheroid( geometry_column,’SPHEROID["GRS_1980",6378137,298.257222101]’ )FROM geometry_table;

SELECT ST_Length_Spheroid( the_geom, sph_m ) As tot_len,ST_Length_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,ST_Length_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2

FROM (SELECT ST_GeomFromText(’MULTILINESTRING((-118.584 38.374,-118.583 38.5),(-71.05957 42.3589 , -71.061 43))’) As the_geom,

CAST(’SPHEROID["GRS_1980",6378137,298.257222101]’ As spheroid) As sph_m) as foo;tot_len | len_line1 | len_line2

------------------+------------------+------------------85204.5207562955 | 13986.8725229309 | 71217.6482333646

--3DSELECT ST_Length_Spheroid( the_geom, sph_m ) As tot_len,ST_Length_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,ST_Length_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2

FROM (SELECT ST_GeomFromEWKT(’MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30) ←↩,

(-71.05957 42.3589 75, -71.061 43 90))’) As the_geom,CAST(’SPHEROID["GRS_1980",6378137,298.257222101]’ As spheroid) As sph_m) as foo;

tot_len | len_line1 | len_line2------------------+-----------------+------------------85204.5259107402 | 13986.876097711 | 71217.6498130292


See Also

ST_GeometryN, ST_Length, ST_3DLength_Spheroid

8.8.34 ST_Length2D_Spheroid

ST_Length2D_Spheroid — Calculates the 2D length of a linestring/multilinestring on an ellipsoid. This is useful if the coordi-nates of the geometry are in longitude/latitude and a length is desired without reprojection.

Synopsis

float ST_Length2D_Spheroid(geometry a_linestring, spheroid a_spheroid);

Description

Calculates the 2D length of a geometry on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitudeand a length is desired without reprojection. The ellipsoid is a separate database type and can be constructed as follows:

SPHEROID[<NAME>,<SEMI-MAJORAXIS>,<INVERSE FLATTENING>]

SPHEROID["GRS_1980",6378137,298.257222101]

NoteWill return 0 for anything that is not a MULTILINESTRING or LINESTRING

NoteThis is much like ST_Length_Spheroid and ST_3DLength_Spheroid except it will throw away the Z coordinate in calcu-lations.

Examples

SELECT ST_Length2D_Spheroid( geometry_column,’SPHEROID["GRS_1980",6378137,298.257222101]’ )FROM geometry_table;

SELECT ST_Length2D_Spheroid( the_geom, sph_m ) As tot_len,ST_Length2D_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,ST_Length2D_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2

FROM (SELECT ST_GeomFromText(’MULTILINESTRING((-118.584 38.374,-118.583 38.5),(-71.05957 42.3589 , -71.061 43))’) As the_geom,

CAST(’SPHEROID["GRS_1980",6378137,298.257222101]’ As spheroid) As sph_m) as foo;tot_len | len_line1 | len_line2

------------------+------------------+------------------85204.5207562955 | 13986.8725229309 | 71217.6482333646

--3D Observe same answerSELECT ST_Length2D_Spheroid( the_geom, sph_m ) As tot_len,ST_Length2D_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,ST_Length2D_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2


FROM (SELECT ST_GeomFromEWKT(’MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30) ←↩,

(-71.05957 42.3589 75, -71.061 43 90))’) As the_geom,CAST(’SPHEROID["GRS_1980",6378137,298.257222101]’ As spheroid) As sph_m) as foo;

tot_len | len_line1 | len_line2------------------+------------------+------------------85204.5207562955 | 13986.8725229309 | 71217.6482333646

See Also

ST_GeometryN, ST_Length_Spheroid, ST_3DLength_Spheroid

8.8.35 ST_3DLength_Spheroid

ST_3DLength_Spheroid — Calculates the length of a geometry on an ellipsoid, taking the elevation into account. This is just analias for ST_Length_Spheroid.

Synopsis

float ST_3DLength_Spheroid(geometry a_linestring, spheroid a_spheroid);

Description

Calculates the length of a geometry on an ellipsoid, taking the elevation into account. This is just an alias for ST_Length_Spheroid.

NoteChanged: 2.0.0 In prior versions this used to return 0 for anything that is not a MULTILINESTRING or LINESTRINGand in 2.0.0 on returns the perimeter of if given a polgon.

NoteThis function is just an alias for ST_Length_Spheroid.


Changed: 2.0.0 In prior versions this used to be called ST_Length3d_Spheroid

Examples

See ST_Length_Spheroid

See Also

ST_GeometryN, ST_Length, ST_Length_Spheroid


8.8.36 ST_LongestLine

ST_LongestLine — Returns the 2-dimensional longest line points of two geometries. The function will only return the firstlongest line if more than one, that the function finds. The line returned will always start in g1 and end in g2. The length of theline this function returns will always be the same as st_maxdistance returns for g1 and g2.

Synopsis

geometry ST_LongestLine(geometry g1, geometry g2);

Description

Returns the 2-dimensional longest line between the points of two geometries.

Availability: 1.5.0

Examples

Longest line between point and line

SELECT ST_AsText(ST_LongestLine(’POINT(100 100)’:: ←↩

geometry,’LINESTRING (20 80, 98 ←↩

190, 110 180, 50 75 )’::geometry)) As lline;

lline-----------------LINESTRING(100 100,98 190)

longest line between polygon and polygon

SELECT ST_AsText(ST_LongestLine(

ST_GeomFromText(’POLYGON ←↩((175 150, 20 40,

50 60, 125 100, ←↩175 150))’),

ST_Buffer(ST_GeomFromText ←↩(’POINT(110 170)’), 20)

)) As llinewkt;

lline-----------------LINESTRING(20 40,121.111404660392 ←↩

186.629392246051)


longest straight distance to travel from one part of an elegant city to the other Note the max distance = to the length of theline.

SELECT ST_AsText(ST_LongestLine(c.the_geom, c.the_geom)) As llinewkt,ST_MaxDistance(c.the_geom,c.the_geom) As max_dist,ST_Length(ST_LongestLine(c.the_geom, c.the_geom)) As lenll

FROM (SELECT ST_BuildArea(ST_Collect(the_geom)) As the_geomFROM (SELECT ST_Translate(ST_SnapToGrid(ST_Buffer(ST_Point(50 ,generate_series ←↩

(50,190, 50)),40, ’quad_segs=2’),1), x, 0) As the_geomFROM generate_series(1,100,50) As x) AS foo

) As c;

llinewkt | max_dist | lenll---------------------------+------------------+------------------LINESTRING(23 22,129 178) | 188.605408193933 | 188.605408193933

See Also

ST_MaxDistance, ST_ShortestLine, ST_LongestLine

8.8.37 ST_OrderingEquals

ST_OrderingEquals — Returns true if the given geometries represent the same geometry and points are in the same directionalorder.

Synopsis

boolean ST_OrderingEquals(geometry A, geometry B);

Description

ST_OrderingEquals compares two geometries and returns t (TRUE) if the geometries are equal and the coordinates are in thesame order; otherwise it returns f (FALSE).


NoteThis function is implemented as per the ArcSDE SQL specification rather than SQL-MM.http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals


Examples

SELECT ST_OrderingEquals(ST_GeomFromText(’LINESTRING(0 0, 10 10)’),ST_GeomFromText(’LINESTRING(0 0, 5 5, 10 10)’));

st_orderingequals-----------f

(1 row)

SELECT ST_OrderingEquals(ST_GeomFromText(’LINESTRING(0 0, 10 10)’),ST_GeomFromText(’LINESTRING(0 0, 0 0, 10 10)’));

st_orderingequals-----------t

(1 row)

SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText(’LINESTRING(0 0, 10 10)’)),ST_GeomFromText(’LINESTRING(0 0, 0 0, 10 10)’));

st_orderingequals-----------f

(1 row)

See Also

ST_Equals, ST_Reverse

8.8.38 ST_Overlaps

ST_Overlaps — Returns TRUE if the Geometries share space, are of the same dimension, but are not completely contained byeach other.

Synopsis

boolean ST_Overlaps(geometry A, geometry B);

Description

Returns TRUE if the Geometries "spatially overlap". By that we mean they intersect, but one does not completely contain another.


NoteDo not call with a GeometryCollection as an argument


This function call will automatically include a bounding box comparison that will make use of any indexes that are available onthe geometries. To avoid index use, use the function _ST_Overlaps.


This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3


Examples

The following illustrations all return TRUE.

MULTIPOINT / MULTIPOINT LINESTRING / LINESTRING POLYGON / POLYGON

--a point on a line is contained by the line and is of a lower dimension, and therefore ←↩does not overlap the line

nor crosses

SELECT ST_Overlaps(a,b) As a_overlap_b,ST_Crosses(a,b) As a_crosses_b,ST_Intersects(a, b) As a_intersects_b, ST_Contains(b,a) As b_contains_a

FROM (SELECT ST_GeomFromText(’POINT(1 0.5)’) As a, ST_GeomFromText(’LINESTRING(1 0, 1 1, 3 ←↩5)’) As b)

As foo

a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a------------+-------------+----------------+--------------f | f | t | t

--a line that is partly contained by circle, but not fully is defined as intersecting and ←↩crossing,

-- but since of different dimension it does not overlapSELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b,

ST_Intersects(a, b) As a_intersects_b,ST_Contains(a,b) As a_contains_b

FROM (SELECT ST_Buffer(ST_GeomFromText(’POINT(1 0.5)’), 3) As a, ST_GeomFromText(’ ←↩LINESTRING(1 0, 1 1, 3 5)’) As b)

As foo;

a_overlap_b | a_crosses_b | a_intersects_b | a_contains_b-------------+-------------+----------------+--------------



f | t | t | f

-- a 2-dimensional bent hot dog (aka buffered line string) that intersects a circle,-- but is not fully contained by the circle is defined as overlapping since they are of ←↩

the same dimension,-- but it does not cross, because the intersection of the 2 is of the same dimension-- as the maximum dimension of the 2

SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b, ST_Intersects(a, b) ←↩As a_intersects_b,

ST_Contains(b,a) As b_contains_a,ST_Dimension(a) As dim_a, ST_Dimension(b) as dim_b, ST_Dimension(ST_Intersection(a,b)) As ←↩

dima_intersection_bFROM (SELECT ST_Buffer(ST_GeomFromText(’POINT(1 0.5)’), 3) As a,

ST_Buffer(ST_GeomFromText(’LINESTRING(1 0, 1 1, 3 5)’),0.5) As b)As foo;

a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a | dim_a | dim_b | ←↩dima_intersection_b

-------------+-------------+----------------+--------------+-------+-------+--------------------- ←↩

t | f | t | f | 2 | 2 | 2

See Also

ST_Contains, ST_Crosses, ST_Dimension, ST_Intersects

8.8.39 ST_Perimeter

ST_Perimeter — Return the length measurement of the boundary of an ST_Surface or ST_MultiSurface geometry or geography.(Polygon, Multipolygon). geometry measurement is in units of spatial reference and geography is in meters.

Synopsis

float ST_Perimeter(geometry g1);

float ST_Perimeter(geography geog, boolean use_spheroid=true);

Description

Returns the 2D perimeter of the geometry/geography if it is a ST_Surface, ST_MultiSurface (Polygon, Multipolygon). 0 isreturned for non-areal geometries. For linestrings use ST_Length. Measurements for geometry are in the units of the spatialreference system of the geometry. Measurements for geography are in meters. If use_spheroid is set to false, then willmodel earth as a sphere instead of a spheroid.

Currently this is an alias for ST_Perimeter2D, but this may change to support higher dimensions.



Availability 2.0.0: Support for geography was introduced



Examples: Geometry

Return perimeter in feet for polygon and multipolygon. Note this is in feet because 2249 is Mass State Plane Feet

SELECT ST_Perimeter(ST_GeomFromText(’POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))’, 2249));st_perimeter---------122.630744000095

(1 row)

SELECT ST_Perimeter(ST_GeomFromText(’MULTIPOLYGON(((763104.471273676 2949418.44119003,763104.477769673 2949418.42538203,763104.189609677 2949418.22343004,763104.471273676 2949418.44119003)),((763104.471273676 2949418.44119003,763095.804579742 2949436.33850239,763086.132105649 2949451.46730207,763078.452329651 2949462.11549407,763075.354136904 2949466.17407812,763064.362142565 2949477.64291974,763059.953961626 2949481.28983009,762994.637609571 2949532.04103014,762990.568508415 2949535.06640477,762986.710889563 2949539.61421415,763117.237897679 2949709.50493431,763235.236617789 2949617.95619822,763287.718121842 2949562.20592617,763111.553321674 2949423.91664605,763104.471273676 2949418.44119003)))’, 2249));st_perimeter---------845.227713366825

(1 row)

Examples: Geography

Return perimeter in meters and feet for polygon and multipolygon. Note this is geography (WGS 84 long lat)

SELECT ST_Perimeter(geog) As per_meters, ST_Perimeter(geog)/0.3048 As per_ftFROM ST_GeogFromText(’POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 ←↩

42.3903829478009,-71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.1776848522251 ←↩

42.3902896512902))’) As geog;

per_meters | per_ft-----------------+------------------37.3790462565251 | 122.634666195949

-- Multipolygon example --SELECT ST_Perimeter(geog) As per_meters, ST_Perimeter(geog,false) As per_sphere_meters, ←↩

ST_Perimeter(geog)/0.3048 As per_ftFROM ST_GeogFromText(’MULTIPOLYGON(((-71.1044543107478 42.340674480411,-71.1044542869917 ←↩

42.3406744369506,-71.1044553562977 42.340673886454,-71.1044543107478 42.340674480411)),((-71.1044543107478 42.340674480411,-71.1044860600303 42.3407237015564,-71.1045215770124 ←↩

42.3407653385914,-71.1045498002983 42.3407946553165,-71.1045611902745 42.3408058316308,-71.1046016507427 ←↩

42.340837442371,-71.104617893173 42.3408475056957,-71.1048586153981 42.3409875993595,-71.1048736143677 ←↩

42.3409959528211,-71.1048878050242 42.3410084812078,-71.1044020965803 42.3414730072048,-71.1039672113619 42.3412202916693,-71.1037740497748 42.3410666421308,-71.1044280218456 42.3406894151355,-71.1044543107478 42.340674480411)))’) As geog;

per_meters | per_sphere_meters | per_ft------------------+-------------------+------------------257.634283683311 | 257.412311446337 | 845.256836231335


See Also

ST_GeogFromText, ST_GeomFromText, ST_Length

8.8.40 ST_Perimeter2D

ST_Perimeter2D — Returns the 2-dimensional perimeter of the geometry, if it is a polygon or multi-polygon. This is currentlyan alias for ST_Perimeter.

Synopsis

float ST_Perimeter2D(geometry geomA);

Description

Returns the 2-dimensional perimeter of the geometry, if it is a polygon or multi-polygon.

NoteThis is currently an alias for ST_Perimeter. In future versions ST_Perimeter may return the highest dimension perimeterfor a geometry. This is still under consideration

See Also

ST_Perimeter

8.8.41 ST_3DPerimeter

ST_3DPerimeter — Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon.

Synopsis

float ST_3DPerimeter(geometry geomA);

Description

Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon. If the geometry is 2-dimensional, thenthe 2-dimensional perimeter is returned.


Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D


Examples

Perimeter of a slightly elevated polygon in the air in Massachusetts state plane feet

SELECT ST_3DPerimeter(the_geom), ST_Perimeter2d(the_geom), ST_Perimeter(the_geom) FROM(SELECT ST_GeomFromEWKT(’SRID=2249;POLYGON((743238 2967416 2,743238 2967450 1,

743265.625 2967416 1,743238 2967416 2))’) As the_geom) As foo;

ST_3DPerimeter | st_perimeter2d | st_perimeter------------------+------------------+------------------105.465793597674 | 105.432997272188 | 105.432997272188

See Also

ST_GeomFromEWKT, ST_Perimeter, ST_Perimeter2D

8.8.42 ST_PointOnSurface

ST_PointOnSurface — Returns a POINT guaranteed to lie on the surface.

Synopsis

geometry ST_PointOnSurface(geometry g1);

Description

Returns a POINT guaranteed to intersect a surface.


This method implements the SQL/MM specification. SQL-MM 3: 8.1.5, 9.5.6. According to the specs, ST_PointOnSurfaceworks for surface geometries (POLYGONs, MULTIPOLYGONS, CURVED POLYGONS). So PostGIS seems to be extendingwhat the spec allows here. Most databases Oracle,DB II, ESRI SDE seem to only support this function for surfaces. SQL Server2008 like PostGIS supports for all common geometries.


Examples

SELECT ST_AsText(ST_PointOnSurface(’POINT(0 5)’::geometry));st_astext

------------POINT(0 5)

(1 row)

SELECT ST_AsText(ST_PointOnSurface(’LINESTRING(0 5, 0 10)’::geometry));st_astext

------------POINT(0 5)

(1 row)

SELECT ST_AsText(ST_PointOnSurface(’POLYGON((0 0, 0 5, 5 5, 5 0, 0 0))’::geometry));



st_astext----------------POINT(2.5 2.5)

(1 row)

SELECT ST_AsEWKT(ST_PointOnSurface(ST_GeomFromEWKT(’LINESTRING(0 5 1, 0 0 1, 0 10 2)’)));st_asewkt

----------------POINT(0 0 1)

(1 row)

See Also

ST_Centroid, ST_Point_Inside_Circle

8.8.43 ST_Project

ST_Project — Returns a POINT projected from a start point using a bearing and distance.

Synopsis

geography ST_Project(geography g1, float distance, float azimuth);

Description

Returns a POINT projected from a start point using an azimuth (bearing) and distance.

Distance, azimuth and projection are all aspects of the same operation, describing (or in the case of projection, constructing) therelationship between two points on the world.

The azimuth is sometimes called the heading or the bearing in navigation. It is measured relative to true north (azimuth zero).East is azimuth 90, south is azimuth 180, west is azimuth 270.

The distance is given in meters.

Examples

SELECT ST_AsText(ST_Project(’POINT(0 0)’::geography, 100000, 45));st_astext

------------------------------------------POINT(0.63523102912532 0.63947233472882)

(1 row)

See Also

ST_Azimuth, ST_Distance

8.8.44 ST_Relate

ST_Relate — Returns true if this Geometry is spatially related to anotherGeometry, by testing for intersections between theInterior, Boundary and Exterior of the two geometries as specified by the values in the intersectionMatrixPattern. If no intersec-tionMatrixPattern is passed in, then returns the maximum intersectionMatrixPattern that relates the 2 geometries.


Synopsis

boolean ST_Relate(geometry geomA, geometry geomB, text intersectionMatrixPattern);text ST_Relate(geometry geomA, geometry geomB);text ST_Relate(geometry geomA, geometry geomB, int BoundaryNodeRule);

Description

Version 1: Takes geomA, geomB, intersectionMatrix and Returns 1 (TRUE) if this Geometry is spatially related to anotherGe-ometry, by testing for intersections between the Interior, Boundary and Exterior of the two geometries as specified by the valuesin the DE-9IM matrix pattern.

This is especially useful for testing compound checks of intersection, crosses, etc in one step.

Do not call with a GeometryCollection as an argument

NoteThis is the "allowable" version that returns a boolean, not an integer. This is defined in OGC spec

NoteThis DOES NOT automagically include an index call. The reason for that is some relationships are anti e.g. Disjoint. Ifyou are using a relationship pattern that requires intersection, then include the && index call.

Version 2: Takes geomA and geomB and returns the Section 4.3.6

Version 3: same as version 2 bu allows to specify a boundary node rule (1:OGC/MOD2, 2:Endpoint, 3:MultivalentEndpoint,4:MonovalentEndpoint)


not in OGC spec, but implied. see s2.1.13.2




Enhanced: 2.0.0 - added support for specifying boundary node rule (requires GEOS >= 3.0).

Examples

--Find all compounds that intersect and not touch a poly (interior intersects)SELECT l.* , b.name As poly_name

FROM polys As bINNER JOIN compounds As lON (p.the_geom && b.the_geomAND ST_Relate(l.the_geom, b.the_geom,’T********’));

http://en.wikipedia.org/wiki/DE-9IM



SELECT ST_Relate(ST_GeometryFromText(’POINT(1 2)’), ST_Buffer(ST_GeometryFromText(’POINT(1 ←↩2)’),2));

st_relate-----------0FFFFF212

SELECT ST_Relate(ST_GeometryFromText(’LINESTRING(1 2, 3 4)’), ST_GeometryFromText(’ ←↩LINESTRING(5 6, 7 8)’));

st_relate-----------FF1FF0102

SELECT ST_Relate(ST_GeometryFromText(’POINT(1 2)’), ST_Buffer(ST_GeometryFromText(’POINT(1 ←↩2)’),2), ’0FFFFF212’);

st_relate-----------t

SELECT ST_Relate(ST_GeometryFromText(’POINT(1 2)’), ST_Buffer(ST_GeometryFromText(’POINT(1 ←↩2)’),2), ’*FF*FF212’);

st_relate-----------t

See Also

ST_Crosses, Section 4.3.6, ST_Disjoint, ST_Intersects, ST_Touches

8.8.45 ST_RelateMatch

ST_RelateMatch — Returns true if intersectionMattrixPattern1 implies intersectionMatrixPattern2

Synopsis

boolean ST_RelateMatch(text intersectionMatrix, text intersectionMatrixPattern);

Description

Takes intersectionMatrix and intersectionMatrixPattern and Returns true if the intersectionMatrix satisfies the intersectionMa-trixPattern. For more information refer to Section 4.3.6.


Examples

SELECT ST_RelateMatch(’101202FFF’, ’TTTTTTFFF’) ;-- result --t--example of common intersection matrix patterns and example matrices-- comparing relationships of involving one invalid geometry and ( a line and polygon that ←↩

intersect at interior and boundary)SELECT mat.name, pat.name, ST_RelateMatch(mat.val, pat.val) As satisfied

FROM( VALUES (’Equality’, ’T1FF1FFF1’),

(’Overlaps’, ’T*T***T**’),


(’Within’, ’T*F**F***’),(’Disjoint’, ’FF*FF****’) As pat(name,val)

CROSS JOIN( VALUES (’Self intersections (invalid)’, ’111111111’),

(’IE2_BI1_BB0_BE1_EI1_EE2’, ’FF2101102’),(’IB1_IE1_BB0_BE0_EI2_EI1_EE2’, ’F11F00212’)

) As mat(name,val);

See Also

Section 4.3.6, ST_Relate

8.8.46 ST_ShortestLine

ST_ShortestLine — Returns the 2-dimensional shortest line between two geometries

Synopsis

geometry ST_ShortestLine(geometry g1, geometry g2);

Description

Returns the 2-dimensional shortest line between two geometries. The function will only return the first shortest line if more thanone, that the function finds. If g1 and g2 intersects in just one point the function will return a line with both start and end in thatintersection-point. If g1 and g2 are intersecting with more than one point the function will return a line with start and end in thesame point but it can be any of the intersecting points. The line returned will always start in g1 and end in g2. The length of theline this function returns will always be the same as st_distance returns for g1 and g2.

Availability: 1.5.0

Examples


Shortest line between point and linestring

SELECT ST_AsText(ST_ShortestLine(’POINT(100 100) ←↩

’::geometry,’LINESTRING (20 80, 98 ←↩190, 110 180, 50 75 )’::geometry)

) As sline;

sline-----------------LINESTRING(100 100,73.0769230769231 ←↩

115.384615384615)

shortest line between polygon and polygon

SELECT ST_AsText(ST_ShortestLine(

ST_GeomFromText(’ ←↩POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))’),

ST_Buffer( ←↩ST_GeomFromText(’POINT(110 170)’), 20)

)) As slinewkt;

LINESTRING(140.752120669087 ←↩125.695053378061,121.111404660392 153.370607753949)

See Also

ST_ClosestPoint, ST_Distance, ST_LongestLine, ST_MaxDistance

8.8.47 ST_Touches

ST_Touches — Returns TRUE if the geometries have at least one point in common, but their interiors do not intersect.

Synopsis

boolean ST_Touches(geometry g1, geometry g2);

Description

Returns TRUE if the only points in common between g1 and g2 lie in the union of the boundaries of g1 and g2. The ST_To-uches relation applies to all Area/Area, Line/Line, Line/Area, Point/Area and Point/Line pairs of relationships, but not to thePoint/Point pair.

In mathematical terms, this predicate is expressed as:


The allowable DE-9IM Intersection Matrices for the two geometries are:

• FT*******

• F**T*****

• F***T****


NoteThis function call will automatically include a bounding box comparison that will make use of any indexes that areavailable on the geometries. To avoid using an index, use _ST_Touches instead.



Examples

The ST_Touches predicate returns TRUE in all the following illustrations.

POLYGON / POLYGON POLYGON / POLYGON POLYGON / LINESTRING



LINESTRING / LINESTRING LINESTRING / LINESTRING POLYGON / POINT

SELECT ST_Touches(’LINESTRING(0 0, 1 1, 0 2)’::geometry, ’POINT(1 1)’::geometry);st_touches

------------f

(1 row)

SELECT ST_Touches(’LINESTRING(0 0, 1 1, 0 2)’::geometry, ’POINT(0 2)’::geometry);st_touches

------------t

(1 row)

8.8.48 ST_Within

ST_Within — Returns true if the geometry A is completely inside geometry B

Synopsis

boolean ST_Within(geometry A, geometry B);

Description

Returns TRUE if geometry A is completely inside geometry B. For this function to make sense, the source geometries must bothbe of the same coordinate projection, having the same SRID. It is a given that if ST_Within(A,B) is true and ST_Within(B,A) istrue, then the two geometries are considered spatially equal.





This function call will automatically include a bounding box comparison that will make use of any indexes that are available onthe geometries. To avoid index use, use the function _ST_Within.


This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 -a.Relate(b, ’T*F**F***’)


Examples

--a circle within a circleSELECT ST_Within(smallc,smallc) As smallinsmall,

ST_Within(smallc, bigc) As smallinbig,ST_Within(bigc,smallc) As biginsmall,ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion

FROM(SELECT ST_Buffer(ST_GeomFromText(’POINT(50 50)’), 20) As smallc,

ST_Buffer(ST_GeomFromText(’POINT(50 50)’), 40) As bigc) As foo;--Resultsmallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion

--------------+------------+------------+------------+------------+------------t | t | f | t | t | t

(1 row)

See Also

ST_Contains, ST_Equals, ST_IsValid



8.9 Geometry Processing

8.9.1 ST_Buffer

ST_Buffer — (T) For geometry: Returns a geometry that represents all points whose distance from this Geometry is lessthan or equal to distance. Calculations are in the Spatial Reference System of this Geometry. For geography: Uses a planartransform wrapper. Introduced in 1.5 support for different end cap and mitre settings to control shape. buffer_style options:quad_segs=#,endcap=round|flat|square,join=round|mitre|bevel,mitre_limit=#.#

Synopsis

geometry ST_Buffer(geometry g1, float radius_of_buffer);geometry ST_Buffer(geometry g1, float radius_of_buffer, integer num_seg_quarter_circle);geometry ST_Buffer(geometry g1, float radius_of_buffer, text buffer_style_parameters);geography ST_Buffer(geography g1, float radius_of_buffer_in_meters);

Description

Returns a geometry/geography that represents all points whose distance from this Geometry/geography is less than or equal todistance.

Geometry: Calculations are in the Spatial Reference System of the geometry. Introduced in 1.5 support for different end cap andmitre settings to control shape.

NoteNegative radii: For polygons, a negative radius can be used, which will shrink the polygon rather than expanding it.

NoteGeography: For geography this is really a thin wrapper around the geometry implementation. It first determines thebest SRID that fits the bounding box of the geography object (favoring UTM, Lambert Azimuthal Equal Area (LAEA)north/south pole, and falling back on mercator in worst case scenario) and then buffers in that planar spatial ref andretransforms back to WGS84 geography.

For geography this may not behave as expected if object is sufficiently large that it falls between two UTM zones or crossesthe dateline

Availability: 1.5 - ST_Buffer was enhanced to support different endcaps and join types. These are useful for example to convertroad linestrings into polygon roads with flat or square edges instead of rounded edges. Thin wrapper for geography was added. -requires GEOS >= 3.2 to take advantage of advanced geometry functionality.

The optional third parameter (currently only applies to geometry) can either specify number of segments used to approximate aquarter circle (integer case, defaults to 8) or a list of blank-separated key=value pairs (string case) to tweak operations as follows:

• ’quad_segs=#’ : number of segments used to approximate a quarter circle (defaults to 8).

• ’endcap=round|flat|square’ : endcap style (defaults to "round", needs GEOS-3.2 or higher for a different value). ’butt’ is alsoaccepted as a synonym for ’flat’.

• ’join=round|mitre|bevel’ : join style (defaults to "round", needs GEOS-3.2 or higher for a different value). ’miter’ is alsoaccepted as a synonym for ’mitre’.

• ’mitre_limit=#.#’ : mitre ratio limit (only affects mitered join style). ’miter_limit’ is also accepted as a synonym for ’mitre_limit’.


Units of radius are measured in units of the spatial reference system.

The inputs can be POINTS, MULTIPOINTS, LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS, andGeometryCollections.

NoteThis function ignores the third dimension (z) and will always give a 2-d buffer even when presented with a 3d-geometry.

Performed by the GEOS module.



NotePeople often make the mistake of using this function to try to do radius searches. Creating a buffer to to a radius searchis slow and pointless. Use ST_DWithin instead.

Examples

quad_segs=8 (default)

SELECT ST_Buffer(ST_GeomFromText(’POINT(100 90)’),50, ’quad_segs=8’);

quad_segs=2 (lame)

SELECT ST_Buffer(ST_GeomFromText(’POINT(100 90)’),50, ’quad_segs=2’);



endcap=round join=round (default)

SELECT ST_Buffer(ST_GeomFromText(’LINESTRING(50 50,150 150,150 50)’

), 10, ’endcap=round join=round’);

endcap=square


), 10, ’endcap=square join=round’);

join=bevel


), 10, ’join=bevel’);

join=mitre mitre_limit=5.0 (default mitre limit)


), 10, ’join=mitre mitre_limit=5.0’);

--A buffered point approximates a circle


-- A buffered point forcing approximation of (see diagram)-- 2 points per circle is poly with 8 sides (see diagram)SELECT ST_NPoints(ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50)) As ←↩

promisingcircle_pcount,ST_NPoints(ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50, 2)) As lamecircle_pcount;

promisingcircle_pcount | lamecircle_pcount------------------------+-------------------

33 | 9

--A lighter but lamer circle-- only 2 points per quarter circle is an octagon--Below is a 100 meter octagon-- Note coordinates are in NAD 83 long lat which we transformto Mass state plane meter and then buffer to get measurements in meters;SELECT ST_AsText(ST_Buffer(ST_Transform(ST_SetSRID(ST_MakePoint(-71.063526, 42.35785),4269), 26986),100,2)) As octagon;----------------------POLYGON((236057.59057465 900908.759918696,236028.301252769 900838.049240578,235957.59057465 900808.759918696,235886.879896532 900838.049240578,235857.59057465900908.759918696,235886.879896532 900979.470596815,235957.59057465 901008.759918696,236028.301252769 900979.470596815,236057.59057465 900908.759918696))

See Also

ST_Collect, ST_DWithin, ST_SetSRID, ST_Transform, ST_Union

8.9.2 ST_BuildArea

ST_BuildArea — Creates an areal geometry formed by the constituent linework of given geometry

Synopsis

geometry ST_BuildArea(geometry A);

Description

Creates an areal geometry formed by the constituent linework of given geometry. The return type can be a Polygon or Multi-Polygon, depending on input. If the input lineworks do not form polygons NULL is returned. The inputs can be LINESTRINGS,MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS, and GeometryCollections.

This function will assume all inner geometries represent holes

NoteInput linework must be correctly noded for this function to work properly


Examples


This will create a donut

SELECT ST_BuildArea(ST_Collect(smallc,bigc))FROM (SELECT

ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 25) As smallc,

ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50) As bigc) As foo;


This will create a gaping hole inside the circle with prongs sticking out

SELECT ST_BuildArea(ST_Collect(line,circle))FROM (SELECT

ST_Buffer(ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)),

5) As line,ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50) As circle) As foo;

--this creates the same gaping hole--but using linestrings instead of polygonsSELECT ST_BuildArea(

ST_Collect(ST_ExteriorRing(line),ST_ExteriorRing(circle)))

FROM (SELECT ST_Buffer(ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190))

,5) As line,ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50) As circle) As foo;

See Also

ST_Node, ST_MakePolygon, ST_BdPolyFromText, ST_BdMPolyFromTextwrappers to this function with standard OGC inter-face

8.9.3 ST_Collect

ST_Collect — Return a specified ST_Geometry value from a collection of other geometries.

Synopsis

geometry ST_Collect(geometry set g1field);geometry ST_Collect(geometry g1, geometry g2);geometry ST_Collect(geometry[] g1_array);


Description

Output type can be a MULTI* or a GEOMETRYCOLLECTION. Comes in 2 variants. Variant 1 collects 2 geometries. Variant2 is an aggregate function that takes a set of geometries and collects them into a single ST_Geometry.

Aggregate version: This function returns a GEOMETRYCOLLECTION or a MULTI object from a set of geometries. TheST_Collect() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows ofdata, in the same way the SUM() and AVG() functions do. For example, "SELECT ST_Collect(GEOM) FROM GEOMTABLEGROUP BY ATTRCOLUMN" will return a separate GEOMETRYCOLLECTION for each distinct value of ATTRCOLUMN.

Non-Aggregate version: This function returns a geometry being a collection of two input geometries. Output type can be aMULTI* or a GEOMETRYCOLLECTION.

NoteST_Collect and ST_Union are often interchangeable. ST_Collect is in general orders of magnitude faster thanST_Union because it does not try to dissolve boundaries or validate that a constructed MultiPolgon doesn’t have over-lapping regions. It merely rolls up single geometries into MULTI and MULTI or mixed geometry types into GeometryCollections. Unfortunately geometry collections are not well-supported by GIS tools. To prevent ST_Collect from re-turning a Geometry Collection when collecting MULTI geometries, one can use the below trick that utilizes ST_Dumpto expand the MULTIs out to singles and then regroup them.

Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.


This method supports Circular Strings and Curves This method supports Circular Strings and Curves, but will never returna MULTICURVE or MULTI as one would expect and PostGIS does not currently support those.

Examples

Aggregate example (http://postgis.refractions.net/pipermail/postgis-users/2008-June/020331.html)

SELECT stusps,ST_Multi(ST_Collect(f.the_geom)) as singlegeom

FROM (SELECT stusps, (ST_Dump(the_geom)).geom As the_geomFROMsomestatetable ) As f

GROUP BY stusps

Non-Aggregate example

SELECT ST_AsText(ST_Collect(ST_GeomFromText(’POINT(1 2)’),ST_GeomFromText(’POINT(-2 3)’) ));

st_astext----------MULTIPOINT(1 2,-2 3)

--Collect 2 d pointsSELECT ST_AsText(ST_Collect(ST_GeomFromText(’POINT(1 2)’),

ST_GeomFromText(’POINT(1 2)’) ) );

st_astext----------MULTIPOINT(1 2,1 2)

--Collect 3d points

http://postgis.refractions.net/pipermail/postgis-users/2008-June/020331.html


SELECT ST_AsEWKT(ST_Collect(ST_GeomFromEWKT(’POINT(1 2 3)’),ST_GeomFromEWKT(’POINT(1 2 4)’) ) );

st_asewkt-------------------------MULTIPOINT(1 2 3,1 2 4)

--Example with curvesSELECT ST_AsText(ST_Collect(ST_GeomFromText(’CIRCULARSTRING(220268 150415,220227 ←↩

150505,220227 150406)’),ST_GeomFromText(’CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)’)));

st_astext------------------------------------------------------------------------------------GEOMETRYCOLLECTION(CIRCULARSTRING(220268 150415,220227 150505,220227 150406),CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))

--New ST_Collect array constructSELECT ST_Collect(ARRAY(SELECT the_geom FROM sometable));

SELECT ST_AsText(ST_Collect(ARRAY[ST_GeomFromText(’LINESTRING(1 2, 3 4)’),ST_GeomFromText(’LINESTRING(3 4, 4 5)’)])) As wktcollect;

--wkt collect --MULTILINESTRING((1 2,3 4),(3 4,4 5))

See Also

ST_Dump, ST_Union

8.9.4 ST_ConcaveHull

ST_ConcaveHull — The concave hull of a geometry represents a possibly concave geometry that encloses all geometries withinthe set. You can think of it as shrink wrapping.

Synopsis

geometry ST_ConcaveHull(geometry geomA, float target_percent, boolean allow_holes=false);

Description

The concave hull of a geometry represents a possibly concave geometry that encloses all geometries within the set. Defaults tofalse for allowing polygons with holes. The result is never higher than a single polygon.

The target_percent is the target percent of area of convex hull the PostGIS solution will try to approach before giving up orexiting. One can think of the concave hull as the geometry you get by vacuum sealing a set of geometries. The target_percentof 1 will give you the same answer as the convex hull. A target_percent between 0 and 0.99 will give you something that shouldhave a smaller area than the convex hull. This is different from a convex hull which is more like wrapping a rubber band aroundthe set of geometries.

It is usually used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction withST_Collect or ST_Union to get the concave hull of a set of points/linestring/polygons ST_ConcaveHull(ST_Collect(somepointfield),0.80).

It is much slower to compute than convex hull but encloses the geometry better and is also useful for image recognition.



NoteNote - If you are using with points, linestrings, or geometry collections use ST_Collect. If you are using with polygons,use ST_Union since it may fail with invalid geometries.

NoteNote - The smaller you make the target percent, the longer it takes to process the concave hull and more likely to runinto topological exceptions. Also the more floating points and number of points you accrue. First try a 0.99 which doesa first hop, is usually very fast, sometimes as fast as computing the convex hull, and usually gives much better than99% of shrink since it almost always overshoots. Second hope of 0.98 it slower, others get slower usually quadratically.To reduce precision and float points, use ST_SimplifyPreserveTopology or ST_SnapToGrid after ST_ConcaveHull.ST_SnapToGrid is a bit faster, but could result in invalid geometries where as ST_SimplifyPreserveTopology almostalways preserves the validity of the geometry.

More real world examples and brief explanation of the technique are shown http://www.bostongis.com/postgis_concavehull.snippet

Also check out Simon Greener’s article on demonstrating ConcaveHull introduced in Oracle 11G R2. http://www.spatialdbadvisor.com/-oracle_spatial_tips_tricks/172/concave-hull-geometries-in-oracle-11gr2. The solution we get at 0.75 target percent of convex hullis similar to the shape Simon gets with Oracle SDO_CONCAVEHULL_BOUNDARY.

Availability: 2.0.0

Examples

--Get estimate of infected area based on point observationsSELECT d.disease_type,

ST_ConcaveHull(ST_Collect(d.pnt_geom), 0.99) As geomFROM disease_obs As dGROUP BY d.disease_type;

http://www.bostongis.com/postgis_concavehull.snippet

http://www.spatialdbadvisor.com/oracle_spatial_tips_tricks/172/concave-hull-geometries-in-oracle-11gr2

http://www.spatialdbadvisor.com/oracle_spatial_tips_tricks/172/concave-hull-geometries-in-oracle-11gr2


ST_ConcaveHull of 2 polygons encased in target 100%shrink concave hull

-- geometries overlaid with concavehull-- at target 100% shrink (this is the ←↩

same as convex hull - since no shrink)SELECT

ST_ConcaveHull(ST_Union(ST_GeomFromText ←↩

(’POLYGON((175 150, 20 40,50 60, 125 100, ←↩

175 150))’),ST_Buffer(ST_GeomFromText ←↩

(’POINT(110 170)’), 20)), 1)

As convexhull;

-- geometries overlaid with concavehull at target 90% ofconvex hull area

-- geometries overlaid with concavehull ←↩at target 90% shrink

SELECTST_ConcaveHull(

ST_Union(ST_GeomFromText ←↩(’POLYGON((175 150, 20 40,

50 60, 125 100, ←↩175 150))’),

ST_Buffer(ST_GeomFromText ←↩(’POINT(110 170)’), 20)

), 0.9)As target_90;


L Shape points overlaid with convex hull

-- this produces a table of 42 points ←↩that form an L shape

SELECT (ST_DumpPoints(ST_GeomFromText(’MULTIPOINT(14 14,34 14,54 14,74 14,94 ←↩

14,114 14,134 14,150 14,154 14,154 6,134 6,114 6,94 6,74 ←↩

6,54 6,34 6,14 6,10 6,8 6,7 7,6 8,6 10,6 30,6 50,6 ←↩

70,6 90,6 110,6 130,6 150,6 170,6 190,6 194,14 194,14 174,14 ←↩

154,14 134,14 114,14 94,14 74,14 54,14 34,14 14)’))).geom

INTO TABLE l_shape;

SELECT ST_ConvexHull(ST_Collect(geom))FROM l_shape;

ST_ConcaveHull of L points at target 99% of convex hull

SELECT ST_ConcaveHull(ST_Collect(geom), ←↩0.99)

FROM l_shape;


Concave Hull of L points at target 80% convex hull area

-- Concave Hull L shape points-- at target 80% of convexhullSELECT ST_ConcaveHull(ST_Collect( ←↩

geom), 0.80)FROM l_shape;

multilinestring overlaid with Convex hull

multilinestring with overlaid with Concave hull oflinestrings at 99% target -- first hop

SELECT ST_ConcaveHull(ST_GeomFromText(’ ←↩MULTILINESTRING((106 164,30 112,74 70,82 112,130 94,

130 62,122 40,156 32,162 76,172 ←↩88),

(132 178,134 148,128 136,96 128,132 ←↩108,150 130,

170 142,174 110,156 96,158 90,158 88),(22 64,66 28,94 38,94 68,114 76,112 30,132 10,168 18,178 34,186 52,184 74,190 ←↩

100,190 122,182 148,178 170,176 184,156 ←↩

164,146 178,132 186,92 182,56 158,36 150,62 150,76 ←↩

128,88 118))’),0.99)


See Also

ST_Collect, ST_ConvexHull, ST_SimplifyPreserveTopology, ST_SnapToGrid

8.9.5 ST_ConvexHull

ST_ConvexHull — The convex hull of a geometry represents the minimum convex geometry that encloses all geometries withinthe set.

Synopsis

geometry ST_ConvexHull(geometry geomA);

Description

The convex hull of a geometry represents the minimum convex geometry that encloses all geometries within the set.

One can think of the convex hull as the geometry you get by wrapping an elastic band around a set of geometries. This is differentfrom a concave hull which is analogous to shrink-wrapping your geometries.

It is usually used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction withST_Collect to get the convex hull of a set of points. ST_ConvexHull(ST_Collect(somepointfield)).

It is often used to determine an affected area based on a set of point observations.





Examples

--Get estimate of infected area based on point observationsSELECT d.disease_type,

ST_ConvexHull(ST_Collect(d.the_geom)) As the_geomFROM disease_obs As dGROUP BY d.disease_type;



Convex Hull of a MultiLinestring and a MultiPoint seen together with the MultiLinestring and MultiPoint

SELECT ST_AsText(ST_ConvexHull(ST_Collect(ST_GeomFromText(’MULTILINESTRING((100 190,10 8),(150 10, 20 30))’),

ST_GeomFromText(’MULTIPOINT(50 5, 150 30, 50 10, 10 10)’))) );

---st_astext--POLYGON((50 5,10 8,10 10,100 190,150 30,150 10,50 5))

See Also

ST_Collect, ST_ConcaveHull, ST_MinimumBoundingCircle

8.9.6 ST_CurveToLine

ST_CurveToLine — Converts a CIRCULARSTRING/CURVEDPOLYGON to a LINESTRING/POLYGON

Synopsis

geometry ST_CurveToLine(geometry curveGeom);geometry ST_CurveToLine(geometry curveGeom, integer segments_per_qtr_circle);

Description

Converst a CIRCULAR STRING to regular LINESTRING or CURVEPOLYGON to POLYGON. Useful for outputting to de-vices that can’t support CIRCULARSTRING geometry types

Converts a given geometry to a linear geometry. Each curved geometry or segment is converted into a linear approximation usingthe default value of 32 segments per quarter circle








Examples

SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText(’CIRCULARSTRING(220268 150415,220227 ←↩150505,220227 150406)’)));

--Result --LINESTRING(220268 150415,220269.95064912 150416.539364228,220271.823415575 ←↩

150418.17258804,220273.613787707 150419.895736857,220275.317452352 150421.704659462,220276.930305234 150423.594998003,220278.448460847 ←↩

150425.562198489,220279.868261823 150427.60152176,220281.186287736 150429.708054909,220282.399363347 ←↩

150431.876723113,220283.50456625 150434.10230186,220284.499233914 150436.379429536,220285.380970099 ←↩

150438.702620341,220286.147650624 150441.066277505,220286.797428488 150443.464706771,220287.328738321 150445.892130112,220287.740300149 ←↩

150448.342699654,220288.031122486 150450.810511759,220288.200504713 150453.289621251,220288.248038775 ←↩

150455.77405574,220288.173610157 150458.257830005,220287.977398166 150460.734960415,220287.659875492 ←↩

150463.199479347,220287.221807076 150465.64544956,220286.664248262 150468.066978495,220285.988542259 ←↩

150470.458232479,220285.196316903 150472.81345077,220284.289480732 150475.126959442,220283.270218395 150477.39318505,220282.140985384 ←↩

150479.606668057,220280.90450212 150481.762075989,220279.5637474 150483.85421628,220278.12195122 ←↩

150485.87804878,220276.582586992 150487.828697901,220274.949363179 150489.701464356,220273.226214362 ←↩

150491.491836488,220271.417291757 150493.195501133,220269.526953216 150494.808354014,220267.559752731 ←↩

150496.326509628,220265.520429459 150497.746310603,220263.41389631 150499.064336517,220261.245228106 ←↩

150500.277412127,220259.019649359 150501.38261503,220256.742521683 150502.377282695,220254.419330878 ←↩

150503.259018879,220252.055673714 150504.025699404,220249.657244448 150504.675477269,220247.229821107 ←↩

150505.206787101,220244.779251566 150505.61834893,220242.311439461 150505.909171266,220239.832329968 ←↩

150506.078553494,220237.347895479 150506.126087555,220234.864121215 150506.051658938,220232.386990804 ←↩

150505.855446946,220229.922471872 150505.537924272,220227.47650166 150505.099855856,220225.054972724 ←↩

150504.542297043,220222.663718741 150503.86659104,220220.308500449 150503.074365683,220217.994991777 150502.167529512,220215.72876617 150501.148267175,220213.515283163 150500.019034164,220211.35987523 150498.7825509,220209.267734939 150497.441796181,220207.243902439 150496,220205.293253319 150494.460635772,220203.420486864 150492.82741196,220201.630114732 ←↩

150491.104263143,220199.926450087 150489.295340538,220198.313597205 150487.405001997,220196.795441592 ←↩

150485.437801511,220195.375640616 150483.39847824,220194.057614703 150481.291945091,220192.844539092 ←↩

150479.123276887,220191.739336189 150476.89769814,220190.744668525 150474.620570464,220189.86293234 150472.297379659,220189.096251815 ←↩

150469.933722495,


220188.446473951 150467.535293229,220187.915164118 150465.107869888,220187.50360229 ←↩150462.657300346,

220187.212779953 150460.189488241,220187.043397726 150457.710378749,220186.995863664 ←↩150455.22594426,

220187.070292282 150452.742169995,220187.266504273 150450.265039585,220187.584026947 ←↩150447.800520653,

220188.022095363 150445.35455044,220188.579654177 150442.933021505,220189.25536018 ←↩150440.541767521,

220190.047585536 150438.18654923,220190.954421707 150435.873040558,220191.973684044 ←↩150433.60681495,

220193.102917055 150431.393331943,220194.339400319 150429.237924011,220195.680155039 ←↩150427.14578372,220197.12195122 150425.12195122,

220198.661315447 150423.171302099,220200.29453926 150421.298535644,220202.017688077 ←↩150419.508163512,220203.826610682 150417.804498867,

220205.716949223 150416.191645986,220207.684149708 150414.673490372,220209.72347298 ←↩150413.253689397,220211.830006129 150411.935663483,

220213.998674333 150410.722587873,220216.22425308 150409.61738497,220218.501380756 ←↩150408.622717305,220220.824571561 150407.740981121,

220223.188228725 150406.974300596,220225.586657991 150406.324522731,220227 150406)

--3d exampleSELECT ST_AsEWKT(ST_CurveToLine(ST_GeomFromEWKT(’CIRCULARSTRING(220268 150415 1,220227 ←↩

150505 2,220227 150406 3)’)));Output------LINESTRING(220268 150415 1,220269.95064912 150416.539364228 1.0181172856673,220271.823415575 150418.17258804 1.03623457133459,220273.613787707 150419.895736857 ←↩

1.05435185700189,....AD INFINITUM ....220225.586657991 150406.324522731 1.32611114201132,220227 150406 3)

--use only 2 segments to approximate quarter circleSELECT ST_AsText(ST_CurveToLine(ST_GeomFromText(’CIRCULARSTRING(220268 150415,220227 ←↩

150505,220227 150406)’),2));st_astext------------------------------LINESTRING(220268 150415,220287.740300149 150448.342699654,220278.12195122 ←↩

150485.87804878,220244.779251566 150505.61834893,220207.243902439 150496,220187.50360229 150462.657300346,220197.12195122 150425.12195122,220227 150406)

See Also

ST_LineToCurve

8.9.7 ST_Difference

ST_Difference — Returns a geometry that represents that part of geometry A that does not intersect with geometry B.

Synopsis

geometry ST_Difference(geometry geomA, geometry geomB);

Description

Returns a geometry that represents that part of geometry A that does not intersect with geometry B. One can think of this asGeometryA - ST_Intersection(A,B). If A is completely contained in B then an empty geometry collection is returned.


NoteNote - order matters. B - A will always return a portion of B





This function supports 3d and will not drop the z-index. However it seems to only consider x y when doing the differenceand tacks back on the Z-Index

Examples

The original linestrings shown together. The difference of the two linestrings

--Safe for 2d. This is same geometries as what is shown for st_symdifferenceSELECT ST_AsText(

ST_Difference(ST_GeomFromText(’LINESTRING(50 100, 50 200)’),ST_GeomFromText(’LINESTRING(50 50, 50 150)’)

));

st_astext



---------LINESTRING(50 150,50 200)

--When used in 3d doesn’t quite do the right thingSELECT ST_AsEWKT(ST_Difference(ST_GeomFromEWKT(’MULTIPOINT(-118.58 38.38 5,-118.60 38.329 ←↩

6,-118.614 38.281 7)’), ST_GeomFromEWKT(’POINT(-118.614 38.281 5)’)));st_asewkt---------MULTIPOINT(-118.6 38.329 6,-118.58 38.38 5)

See Also

ST_SymDifference

8.9.8 ST_Dump

ST_Dump — Returns a set of geometry_dump (geom,path) rows, that make up a geometry g1.

Synopsis

geometry_dump[] ST_Dump(geometry g1);

Description

This is a set-returning function (SRF). It returns a set of geometry_dump rows, formed by a geometry (geom) and an array ofintegers (path). When the input geometry is a simple type (POINT,LINESTRING,POLYGON) a single record will be returnedwith an empty path array and the input geometry as geom. When the input geometry is a collection or multi it will return a recordfor each of the collection components, and the path will express the position of the component inside the collection.

ST_Dump is useful for expanding geometries. It is the reverse of a GROUP BY in that it creates new rows. For example it canbe use to expand MULTIPOLYGONS into POLYGONS.


Availability: PostGIS 1.0.0RC1. Requires PostgreSQL 7.3 or higher.







Standard Examples

SELECT sometable.field1, sometable.field1,(ST_Dump(sometable.the_geom)).geom AS the_geom

FROM sometable;

-- Break a compound curve into its constituent linestrings and circularstringsSELECT ST_AsEWKT(a.geom), ST_HasArc(a.geom)

FROM ( SELECT (ST_Dump(p_geom)).geom AS geomFROM (SELECT ST_GeomFromEWKT(’COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 ←↩

1))’) AS p_geom) AS b) AS a;st_asewkt | st_hasarc

-----------------------------+----------CIRCULARSTRING(0 0,1 1,1 0) | tLINESTRING(1 0,0 1) | f

(2 rows)


-- Polyhedral surface example-- Break a Polyhedral surface into its facesSELECT (a.p_geom).path[1] As path, ST_AsEWKT((a.p_geom).geom) As geom_ewkt

FROM (SELECT ST_Dump(ST_GeomFromEWKT(’POLYHEDRALSURFACE(((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 ←↩

1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)))’) ) AS p_geom ) AS a;

path | geom_ewkt------+------------------------------------------

1 | POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0))2 | POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))3 | POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))4 | POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0))5 | POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0))6 | POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))

-- TIN --SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt

FROM(SELECT

ST_Dump( ST_GeomFromEWKT(’TIN (((0 0 0,0 0 1,0 1 0,0 0 0

)), ((0 0 0,0 1 0,1 1 0,0 0 0

)))’) ) AS gdump

) AS g;-- result --path | wkt

------+-------------------------------------


{1} | TRIANGLE((0 0 0,0 0 1,0 1 0,0 0 0)){2} | TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

See Also

geometry_dump, Section 13.5, ST_Collect, ST_Collect, ST_GeometryN

8.9.9 ST_DumpPoints

ST_DumpPoints — Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.

Synopsis

geometry_dump[]ST_DumpPoints(geometry geom);

Description

This set-returning function (SRF) returns a set of geometry_dump rows formed by a geometry (geom) and an array of integers(path).

The geom component of geometry_dump are all the POINTs that make up the supplied geometry

The path component of geometry_dump (an integer[]) is an index reference enumerating the POINTs of the suppliedgeometry. For example, if a LINESTRING is supplied, a path of {i} is returned where i is the nth coordinate in the LINES-TRING. If a POLYGON is supplied, a path of {i,j} is returned where i is the ring number (1 is outer; inner rings follow) andj enumerates the POINTs (again 1-based index).


Availability: 1.5.0





Classic Explode a Table of LineStrings into nodes

SELECT edge_id, (dp).path[1] As index, ST_AsText((dp).geom) As wktnodeFROM (SELECT 1 As edge_id

, ST_DumpPoints(ST_GeomFromText(’LINESTRING(1 2, 3 4, 10 10)’)) AS dpUNION ALLSELECT 2 As edge_id

, ST_DumpPoints(ST_GeomFromText(’LINESTRING(3 5, 5 6, 9 10)’)) AS dp) As foo;

edge_id | index | wktnode---------+-------+--------------

1 | 1 | POINT(1 2)1 | 2 | POINT(3 4)1 | 3 | POINT(10 10)2 | 1 | POINT(3 5)2 | 2 | POINT(5 6)2 | 3 | POINT(9 10)


Standard Geometry Examples

SELECT path, ST_AsText(geom)FROM (

SELECT (ST_DumpPoints(g.geom)).*FROM(SELECT

’GEOMETRYCOLLECTION(POINT ( 0 1 ),LINESTRING ( 0 3, 3 4 ),POLYGON (( 2 0, 2 3, 0 2, 2 0 )),POLYGON (( 3 0, 3 3, 6 3, 6 0, 3 0 ),

( 5 1, 4 2, 5 2, 5 1 )),MULTIPOLYGON (

(( 0 5, 0 8, 4 8, 4 5, 0 5 ),( 1 6, 3 6, 2 7, 1 6 )),

(( 5 4, 5 8, 6 7, 5 4 )))

)’::geometry AS geom) AS g

) j;

path | st_astext-----------+------------{1,1} | POINT(0 1){2,1} | POINT(0 3){2,2} | POINT(3 4){3,1,1} | POINT(2 0){3,1,2} | POINT(2 3){3,1,3} | POINT(0 2){3,1,4} | POINT(2 0){4,1,1} | POINT(3 0){4,1,2} | POINT(3 3){4,1,3} | POINT(6 3){4,1,4} | POINT(6 0){4,1,5} | POINT(3 0){4,2,1} | POINT(5 1){4,2,2} | POINT(4 2){4,2,3} | POINT(5 2){4,2,4} | POINT(5 1){5,1,1,1} | POINT(0 5){5,1,1,2} | POINT(0 8)


{5,1,1,3} | POINT(4 8){5,1,1,4} | POINT(4 5){5,1,1,5} | POINT(0 5){5,1,2,1} | POINT(1 6){5,1,2,2} | POINT(3 6){5,1,2,3} | POINT(2 7){5,1,2,4} | POINT(1 6){5,2,1,1} | POINT(5 4){5,2,1,2} | POINT(5 8){5,2,1,3} | POINT(6 7){5,2,1,4} | POINT(5 4)

(29 rows)


-- Polyhedral surface cube --SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt

FROM(SELECT

ST_DumpPoints(ST_GeomFromEWKT(’POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 ←↩0)),

((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )’) ) AS gdump

) AS g;-- result --

path | wkt---------+--------------{1,1,1} | POINT(0 0 0){1,1,2} | POINT(0 0 1){1,1,3} | POINT(0 1 1){1,1,4} | POINT(0 1 0){1,1,5} | POINT(0 0 0){2,1,1} | POINT(0 0 0){2,1,2} | POINT(0 1 0){2,1,3} | POINT(1 1 0){2,1,4} | POINT(1 0 0){2,1,5} | POINT(0 0 0){3,1,1} | POINT(0 0 0){3,1,2} | POINT(1 0 0){3,1,3} | POINT(1 0 1){3,1,4} | POINT(0 0 1){3,1,5} | POINT(0 0 0){4,1,1} | POINT(1 1 0){4,1,2} | POINT(1 1 1){4,1,3} | POINT(1 0 1){4,1,4} | POINT(1 0 0){4,1,5} | POINT(1 1 0){5,1,1} | POINT(0 1 0){5,1,2} | POINT(0 1 1){5,1,3} | POINT(1 1 1){5,1,4} | POINT(1 1 0){5,1,5} | POINT(0 1 0){6,1,1} | POINT(0 0 1){6,1,2} | POINT(1 0 1){6,1,3} | POINT(1 1 1){6,1,4} | POINT(0 1 1){6,1,5} | POINT(0 0 1)

(30 rows)


-- Triangle --SELECT (g.gdump).path, ST_AsText((g.gdump).geom) as wkt

FROM(SELECT

ST_DumpPoints( ST_GeomFromEWKT(’TRIANGLE ((0 0,0 9,9 0,0 0

))’) ) AS gdump) AS g;

-- result --path | wkt

------+------------{1} | POINT(0 0){2} | POINT(0 9){3} | POINT(9 0){4} | POINT(0 0)

-- TIN --SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt

FROM(SELECT

ST_DumpPoints( ST_GeomFromEWKT(’TIN (((0 0 0,0 0 1,0 1 0,0 0 0

)), ((0 0 0,0 1 0,1 1 0,0 0 0

)))’) ) AS gdump

) AS g;-- result --

path | wkt---------+--------------{1,1,1} | POINT(0 0 0){1,1,2} | POINT(0 0 1){1,1,3} | POINT(0 1 0){1,1,4} | POINT(0 0 0){2,1,1} | POINT(0 0 0){2,1,2} | POINT(0 1 0){2,1,3} | POINT(1 1 0){2,1,4} | POINT(0 0 0)

(8 rows)

See Also

geometry_dump, Section 13.5, ST_Dump, ST_DumpRings

8.9.10 ST_DumpRings

ST_DumpRings — Returns a set of geometry_dump rows, representing the exterior and interior rings of a polygon.


Synopsis

geometry_dump[] ST_DumpRings(geometry a_polygon);

Description

This is a set-returning function (SRF). It returns a set of geometry_dump rows, defined as an integer[] and a geometry,aliased "path" and "geom" respectively. The "path" field holds the polygon ring index containing a single integer: 0 for the shell,>0 for holes. The "geom" field contains the corresponding ring as a polygon.

Availability: PostGIS 1.1.3. Requires PostgreSQL 7.3 or higher.

NoteThis only works for POLYGON geometries. It will not work for MULTIPOLYGONS


Examples

SELECT sometable.field1, sometable.field1,(ST_DumpRings(sometable.the_geom)).geom As the_geom

FROM sometableOfpolys;

SELECT ST_AsEWKT(geom) As the_geom, pathFROM ST_DumpRings(ST_GeomFromEWKT(’POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 ←↩

1,-8148972 5132767 1,-8148958 5132508 1,-8148941 5132466 1,-8148924 5132394 1,-8148903 5132210 1,-8148930 5131967 1,-8148992 5131978 1,-8149237 5132093 1,-8149404 ←↩

5132211 1,-8149647 5132310 1,-8149757 5132394 1,-8150305 5132788 1,-8149064 5133092 1),(-8149362 5132394 1,-8149446 5132501 1,-8149548 5132597 1,-8149695 5132675 1,-8149362 ←↩

5132394 1))’)) as foo;

path | the_geom---------------------------------------------------------------------------------------------------------------- ←↩

{0} | POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 ←↩1,-8148958 5132508 1,

| -8148941 5132466 1,-8148924 5132394 1,| -8148903 5132210 1,-8148930 5131967 1,| -8148992 5131978 1,-8149237 5132093 1,| -8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,-8150305 5132788 ←↩

1,-8149064 5133092 1)){1} | POLYGON((-8149362 5132394 1,-8149446 5132501 1,| -8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))

See Also

geometry_dump, Section 13.5, ST_Dump, ST_ExteriorRing, ST_InteriorRingN

8.9.11 ST_FlipCoordinates

ST_FlipCoordinates — Returns a version of the given geometry with X and Y axis flipped. Useful for people who have builtlatitude/longitude features and need to fix them.


Synopsis

geometry ST_FlipCoordinates(geometry geom);

Description

Returns a version of the given geometry with X and Y axis flipped.



This function supports M coordinates.

Availability: 2.0.0



Example

SELECT ST_AsEWKT(ST_FlipCoordinates(GeomFromEWKT(’POINT(1 2)’)));st_asewkt

------------POINT(2 1)

8.9.12 ST_Intersection

ST_Intersection — (T) Returns a geometry that represents the shared portion of geomA and geomB. The geography implemen-tation does a transform to geometry to do the intersection and then transform back to WGS84.

Synopsis

geometry ST_Intersection( geometry geomA , geometry geomB );geography ST_Intersection( geography geogA , geography geogB );

Description

Returns a geometry that represents the point set intersection of the Geometries.

In other words - that portion of geometry A and geometry B that is shared between the two geometries.

If the geometries do not share any space (are disjoint), then an empty geometry collection is returned.

ST_Intersection in conjunction with ST_Intersects is very useful for clipping geometries such as in bounding box, buffer, regionqueries where you only want to return that portion of a geometry that sits in a country or region of interest.

NoteGeography: For geography this is really a thin wrapper around the geometry implementation. It first determines thebest SRID that fits the bounding box of the 2 geography objects (if geography objects are within one half zone UTM butnot same UTM will pick one of those) (favoring UTM or Lambert Azimuthal Equal Area (LAEA) north/south pole, andfalling back on mercator in worst case scenario) and then intersection in that best fit planar spatial ref and retransformsback to WGS84 geography.




Availability: 1.5 support for geography data type was introduced.



Examples

SELECT ST_AsText(ST_Intersection(’POINT(0 0)’::geometry, ’LINESTRING ( 2 0, 0 2 )’:: ←↩geometry));

st_astext---------------GEOMETRYCOLLECTION EMPTY(1 row)SELECT ST_AsText(ST_Intersection(’POINT(0 0)’::geometry, ’LINESTRING ( 0 0, 0 2 )’:: ←↩

geometry));st_astext

---------------POINT(0 0)(1 row)

---Clip all lines (trails) by country (here we assume country geom are POLYGON or ←↩MULTIPOLYGONS)

-- NOTE: we are only keeping intersections that result in a LINESTRING or MULTILINESTRING ←↩because we don’t

-- care about trails that just share a point-- the dump is needed to expand a geometry collection into individual single MULT* parts-- the below is fairly generic and will work for polys, etc. by just changing the where ←↩

clauseSELECT clipped.gid, clipped.f_name, clipped_geomFROM (SELECT trails.gid, trails.f_name, (ST_Dump(ST_Intersection(country.the_geom, trails. ←↩

the_geom))).geom As clipped_geomFROM country

INNER JOIN trailsON ST_Intersects(country.the_geom, trails.the_geom)) As clippedWHERE ST_Dimension(clipped.clipped_geom) = 1 ;

--For polys e.g. polygon landmarks, you can also use the sometimes faster hack that ←↩buffering anything by 0.0

-- except a polygon results in an empty geometry collection--(so a geometry collection containing polys, lines and points)-- buffered by 0.0 would only leave the polygons and dissolve the collection shellSELECT poly.gid, ST_Multi(ST_Buffer(

ST_Intersection(country.the_geom, poly.the_geom),0.0)) As clipped_geom

FROM countryINNER JOIN polyON ST_Intersects(country.the_geom, poly.the_geom)WHERE Not ST_IsEmpty(ST_Buffer(ST_Intersection(country.the_geom, poly.the_geom),0.0));



See Also

ST_Difference, ST_Dimension, ST_Dump, ST_SymDifference, ST_Intersects, ST_Multi

8.9.13 ST_LineToCurve

ST_LineToCurve — Converts a LINESTRING/POLYGON to a CIRCULARSTRING, CURVED POLYGON

Synopsis

geometry ST_LineToCurve(geometry geomANoncircular);

Description

Converts plain LINESTRING/POLYGONS to CIRCULAR STRINGs and Curved Polygons. Note much fewer points are neededto describe the curved equivalent.




Examples

SELECT ST_AsText(ST_LineToCurve(foo.the_geom)) As curvedastext,ST_AsText(foo.the_geom) As ←↩non_curvedastext

FROM (SELECT ST_Buffer(’POINT(1 3)’::geometry, 3) As the_geom) As foo;

curvedatext non_curvedastext--------------------------------------------------------------------|----------------------------------------------------------------- ←↩

CURVEPOLYGON(CIRCULARSTRING(4 3,3.12132034355964 0.878679656440359, | POLYGON((4 ←↩3,3.94235584120969 2.41472903395162,3.77163859753386 1.85194970290473,

1 0,-1.12132034355965 5.12132034355963,4 3)) | 3.49440883690764 ←↩1.33328930094119,3.12132034355964 0.878679656440359,

| 2.66671069905881 ←↩0.505591163092366,2.14805029709527 ←↩0.228361402466141,

| 1.58527096604839 ←↩0.0576441587903094,1 ←↩0,

| 0.414729033951621 ←↩0.0576441587903077,-0.148050297095264 ←↩0.228361402466137,

| -0.666710699058802 ←↩0.505591163092361,-1.12132034355964 ←↩0.878679656440353,

| -1.49440883690763 ←↩1.33328930094119,-1.77163859753386 ←↩1.85194970290472

| --ETC-- ←↩,3.94235584120969 ←↩3.58527096604839,4 ←↩3))

--3D example


SELECT ST_AsEWKT(ST_LineToCurve(ST_GeomFromEWKT(’LINESTRING(1 2 3, 3 4 8, 5 6 4, 7 8 4, 9 ←↩10 4)’)));

st_asewkt------------------------------------CIRCULARSTRING(1 2 3,5 6 4,9 10 4)

See Also

ST_CurveToLine

8.9.14 ST_MakeValid

ST_MakeValid — Attempts to make an invalid geometry valid w/out loosing vertices.

Synopsis

geometry ST_MakeValid(geometry input);

Description

The function attempts to create a valid representation of a given invalid geometry without loosing any of the input vertices.Already-valid geometries are returned w/out further intervention.

Supported inputs are: LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS.

In case of full or partial dimensional collapses, the output geometry may be a collection of lower-to-equal dimension geometriesor a geometry of lower dimension.

Single polygons may become multi-geometries in case of self-intersections.

Availability: 2.0.0, requires GEOS-3.3.0 or higher.


See Also

ST_IsValid ST_CollectionExtract

8.9.15 ST_MemUnion

ST_MemUnion — Same as ST_Union, only memory-friendly (uses less memory and more processor time).

Synopsis

geometry ST_MemUnion(geometry set geomfield);


Description

Some useful description here.

NoteSame as ST_Union, only memory-friendly (uses less memory and more processor time). This aggregate function worksby unioning the geometries one at a time to previous result as opposed to ST_Union aggregate which first creates anarray and then unions


Examples

See ST_Union

See Also

ST_Union

8.9.16 ST_MinimumBoundingCircle

ST_MinimumBoundingCircle — Returns the smallest circle polygon that can fully contain a geometry. Default uses 48 segmentsper quarter circle.

Synopsis

geometry ST_MinimumBoundingCircle(geometry geomA, integer num_segs_per_qt_circ=48);

Description

Returns the smallest circle polygon that can fully contain a geometry.

NoteThe circle is approximated by a polygon with a default of 48 segments per quarter circle. This number can be increasedwith little performance penalty to obtain a more accurate result.

It is often used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction withST_Collect to get the minimum bounding circle of a set of geometries. ST_MinimumBoundingCircle(ST_Collect(somepointfield)).

The ratio of the area of a polygon divided by the area of its Minimum Bounding Circle is often referred to as the Roeck test.

Availability: 1.4.0 - requires GEOS


Examples

SELECT d.disease_type,ST_MinimumBoundingCircle(ST_Collect(d.the_geom)) As the_geomFROM disease_obs As dGROUP BY d.disease_type;

Minimum bounding circle of a point and linestring. Using 8 segs to approximate a quarter circle

SELECT ST_AsText(ST_MinimumBoundingCircle(ST_Collect(

ST_GeomFromEWKT(’LINESTRING(55 75,125 150)’),ST_Point(20, 80)), 8)) As wktmbc;

wktmbc-----------POLYGON((135.59714732062 115,134.384753327498 102.690357210921,130.79416296937 ←↩

90.8537670908995,124.963360620072 79.9451031602111,117.116420743937 ←↩70.3835792560632,107.554896839789 62.5366393799277,96.6462329091006 ←↩56.70583703063,84.8096427890789 53.115246672502,72.5000000000001 ←↩51.9028526793802,60.1903572109213 53.1152466725019,48.3537670908996 ←↩56.7058370306299,37.4451031602112 62.5366393799276,27.8835792560632 ←↩70.383579256063,20.0366393799278 79.9451031602109,14.20583703063 ←↩90.8537670908993,10.615246672502 102.690357210921,9.40285267938019 115,10.6152466725019 ←↩127.309642789079,14.2058370306299 139.1462329091,20.0366393799275 ←↩150.054896839789,27.883579256063 159.616420743937,

37.4451031602108 167.463360620072,48.3537670908992 173.29416296937,60.190357210921 ←↩176.884753327498,

72.4999999999998 178.09714732062,84.8096427890786 176.884753327498,96.6462329091003 ←↩173.29416296937,107.554896839789 167.463360620072,

117.116420743937 159.616420743937,124.963360620072 150.054896839789,130.79416296937 ←↩139.146232909101,134.384753327498 127.309642789079,135.59714732062 115))

See Also

ST_Collect, ST_ConvexHull


8.9.17 ST_Polygonize

ST_Polygonize — Aggregate. Creates a GeometryCollection containing possible polygons formed from the constituent lineworkof a set of geometries.

Synopsis

geometry ST_Polygonize(geometry set geomfield);geometry ST_Polygonize(geometry[] geom_array);

Description

Creates a GeometryCollection containing possible polygons formed from the constituent linework of a set of geometries.

NoteGeometry Collections are often difficult to deal with with third party tools, so use ST_Polygonize in conjunction withST_Dump to dump the polygons out into individual polygons.

NoteInput linework must be correctly noded for this function to work properly

Availability: 1.0.0RC1 - requires GEOS >= 2.1.0.

Examples: Polygonizing single linestrings

SELECT ST_AsEWKT(ST_Polygonize(the_geom_4269)) As geomtextrepFROM (SELECT the_geom_4269 FROM ma.suffolk_edges ORDER BY tlid LIMIT 45) As foo;

geomtextrep-------------------------------------SRID=4269;GEOMETRYCOLLECTION(POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 ←↩

42.285752,-71.040878 42.285678)),POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358,-71.171794 ←↩

42.354971,-71.170511 42.354855,-71.17112 42.354238,-71.17166 42.353675)))

(1 row)

--Use ST_Dump to dump out the polygonize geoms into individual polygonsSELECT ST_AsEWKT((ST_Dump(foofoo.polycoll)).geom) As geomtextrepFROM (SELECT ST_Polygonize(the_geom_4269) As polycoll

FROM (SELECT the_geom_4269 FROM ma.suffolk_edgesORDER BY tlid LIMIT 45) As foo) As foofoo;

geomtextrep------------------------SRID=4269;POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,

-71.040878 42.285678))SRID=4269;POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358

,-71.171794 42.354971,-71.170511 42.354855,-71.17112 42.354238,-71.17166 42.353675))(2 rows)


See Also

ST_Node, ST_Dump

8.9.18 ST_Node

ST_Node — Node a set of linestrings.

Synopsis

geometry ST_Node(geometry geom);

Description

Fully node a set of linestrings using the least possible number of nodes while preserving all of the input ones.



NoteDue to a bug in GEOS up to 3.3.1 this function fails to node self-intersecting lines. This is fixed with GEOS 3.3.2 orhigher.

Examples

SELECT ST_AsEWKT(ST_Node(’LINESTRINGZ(0 0 0, 10 10 10, 0 10 5, 10 0 3)’::geometry)

) As output;output-----------MULTILINESTRING((0 0 0,5 5 4.5),(5 5 4.5,10 10 10,0 10 5,5 5 4.5),(5 5 4.5,10 0 3))

See Also

ST_UnaryUnion

8.9.19 ST_OffsetCurve

ST_OffsetCurve — Return an offset line at a given distance and side from an input line. Useful for computing parallel linesabout a center line

Synopsis

geometry ST_OffsetCurve(geometry line, float signed_distance, text style_parameters=”);


Description

Return an offset line at a given distance and side from an input line. All points of the returned geometries are not further than thegiven distance from the input geometry.

For positive distance the offset will be at the left side of the input line and retain the same direction. For a negative distance it’llbe at the right side and in the opposite direction.

Availability: 2.0 - requires GEOS >= 3.2, improved with GEOS >= 3.3

The optional third parameter allows specifying a list of blank-separated key=value pairs to tweak operations as follows:

• ’quad_segs=#’ : number of segments used to approximate a quarter circle (defaults to 8).

• ’join=round|mitre|bevel’ : join style (defaults to "round"). ’miter’ is also accepted as a synonym for ’mitre’.

• ’mitre_limit=#.#’ : mitre ratio limit (only affects mitred join style). ’miter_limit’ is also accepted as a synonym for ’mitre_limit’.

Units of distance are measured in units of the spatial reference system.

The inputs can only be LINESTRINGS.

Performed by the GEOS module.

NoteThis function ignores the third dimension (z) and will always give a 2-d result even when presented with a 3d-geometry.

Examples

Compute an open buffer around roads

SELECT ST_Union(ST_OffsetCurve(f.the_geom, f.width/2, ’quad_segs=4 join=round’),ST_OffsetCurve(f.the_geom, -f.width/2, ’quad_segs=4 join=round’)

) as trackFROM someroadstable;


15, ’quad_segs=4 join=round’ original line and its offset 15units.

SELECT ST_AsText(ST_OffsetCurve( ←↩ST_GeomFromText(

’LINESTRING(164 16,144 16,124 16,104 ←↩16,84 16,64 16,

44 16,24 16,20 16,18 16,17 17,16 18,16 20,16 40,16 60,16 80,16 ←↩

100,16 120,16 140,16 160,16 180,16 ←↩

195)’),15, ’quad_segs=4 join=round’));

--output --LINESTRING(164 1,18 1,12.2597485145237 ←↩

2.1418070123307,7.39339828220179 ←↩

5.39339828220179,5.39339828220179 ←↩

7.39339828220179,2.14180701233067 ←↩

12.2597485145237,1 18,1 195)

-15, ’quad_segs=4 join=round’ original line and its offset-15 units

SELECT ST_AsText(ST_OffsetCurve(geom,-15, ’quad_segs=4 join=round’)) ←↩

As notsocurvyFROM ST_GeomFromText(

’LINESTRING(164 16,144 16,124 16,104 ←↩16,84 16,64 16,

44 16,24 16,20 16,18 16,17 17,16 18,16 20,16 40,16 60,16 80,16 ←↩

100,16 120,16 140,16 160,16 180,16 ←↩

195)’) As geom;-- notsocurvy --LINESTRING(31 195,31 31,164 31)


double-offset to get more curvy, note the first reversesdirection, so -30 + 15 = -15

SELECT ST_AsText(ST_OffsetCurve( ←↩ST_OffsetCurve(geom,

-30, ’quad_segs=4 join=round’), ←↩-15, ’quad_segs=4 join=round’)) As morecurvy

FROM ST_GeomFromText(’LINESTRING(164 16,144 16,124 16,104 ←↩

16,84 16,64 16,44 16,24 16,20 16,18 16,17 17,16 18,16 20,16 40,16 60,16 80,16 ←↩

100,16 120,16 140,16 160,16 180,16 ←↩

195)’) As geom;-- morecurvy --LINESTRING(164 31,46 31,40.2597485145236 ←↩

32.1418070123307,35.3933982822018 35.3933982822018,32.1418070123307 40.2597485145237,31 ←↩

46,31 195)

double-offset to get more curvy,combined with regularoffset 15 to get parallel lines. Overlaid with original.

SELECT ST_AsText(ST_Collect(ST_OffsetCurve(geom, 15, ’ ←↩

quad_segs=4 join=round’),ST_OffsetCurve(ST_OffsetCurve( ←↩

geom,-30, ’quad_segs=4 join=round’), ←↩

-15, ’quad_segs=4 join=round’))

) As parallel_curvesFROM ST_GeomFromText(

’LINESTRING(164 16,144 16,124 16,104 ←↩16,84 16,64 16,

44 16,24 16,20 16,18 16,17 17,16 18,16 20,16 40,16 60,16 80,16 ←↩

100,16 120,16 140,16 160,16 180,16 ←↩

195)’) As geom;-- parallel curves --MULTILINESTRING((164 1,18 ←↩

1,12.2597485145237 2.1418070123307,7.39339828220179 ←↩

5.39339828220179,5.39339828220179 7.39339828220179,2.14180701233067 12.2597485145237,1 18,1 ←↩

195),(164 31,46 31,40.2597485145236 ←↩

32.1418070123307,35.3933982822018 35.3933982822018,32.1418070123307 40.2597485145237,31 ←↩

46,31 195))


15, ’quad_segs=4 join=bevel’ shown with original line

SELECT ST_AsText(ST_OffsetCurve( ←↩ST_GeomFromText(

’LINESTRING(164 16,144 16,124 16,104 ←↩16,84 16,64 16,

44 16,24 16,20 16,18 16,17 17,16 18,16 20,16 40,16 60,16 80,16 ←↩

100,16 120,16 140,16 160,16 180,16 ←↩

195)’),15, ’quad_segs=4 join= ←↩

bevel’));-- output --LINESTRING(164 1,18 1,7.39339828220179 ←↩

5.39339828220179,5.39339828220179 ←↩

7.39339828220179,1 18,1 195)

15,-15 collected, join=mitre mitre_limit=2.1

SELECT ST_AsText(ST_Collect(ST_OffsetCurve(geom, 15, ’ ←↩

quad_segs=4 join=mitre mitre_limit=2.2’),ST_OffsetCurve(geom, -15, ’ ←↩

quad_segs=4 join=mitre mitre_limit=2.2’)) )FROM ST_GeomFromText(

’LINESTRING(164 16,144 16,124 16,104 ←↩16,84 16,64 16,

44 16,24 16,20 16,18 16,17 17,16 18,16 20,16 40,16 60,16 80,16 ←↩

100,16 120,16 140,16 160,16 180,16 ←↩

195)’) As geom;-- output --MULTILINESTRING((164 1,11.7867965644036 ←↩

1,1 11.7867965644036,1 195),(31 195,31 31,164 31))

See Also

ST_Buffer

8.9.20 ST_RemoveRepeatedPoints

ST_RemoveRepeatedPoints — Returns a version of the given geometry with duplicated points removed.

Synopsis

geometry ST_RemoveRepeatedPoints(geometry geom);


Description

Returns a version of the given geometry with duplicated points removed. Will actually do something only with (multi)lines,(multi)polygons and multipoints but you can safely call it with any kind of geometry. Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.

Availability: 2.0.0



See Also

ST_Simplify

8.9.21 ST_SharedPaths

ST_SharedPaths — Returns a collection containing paths shared by the two input linestrings/multilinestrings.

Synopsis

geometry ST_SharedPaths(geometry lineal1, geometry lineal2);

Description

Returns a collection containing paths shared by the two input geometries. Those going in the same direction are in the firstelement of the collection, those going in the opposite direction are in the second element. The paths themselves are given in thedirection of the first geometry.

Availability: 2.0.0 requires GEOS >= 3.3.0.

Examples: Finding shared paths

A multilinestring and a linestring

Documents

PostGIS 2.0.2 Manual · PostGIS 2.0.2 Manual iii 3 PostGIS Frequently Asked Questions 20 4 Using PostGIS: Data Management and Queries24 4.1 GIS Objects

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